Shopping tools

Abstract

To provide a driving tool which can stabilize a stop position of a plunger.SOLUTION: A driving tool includes: a plunger; a motor for moving the plunger from a bottom dead point to a top dead point; driving means for driving a fastener using the plunger by moving the plunger from the top dead point to the bottom dead point; voltage fluctuation information acquisition means for acquiring voltage fluctuation information indicating fluctuation amount of voltage applied to the motor during the movement of the plunger from the bottom dead point to the top dead point; and control means for controlling the motor on the basis of the voltage fluctuation information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a driving tool. [Background technology]

[0002] 2. Description of the Related Art Driving tools are known that use a motor to drive a plunger to drive nails, tacks, staples, pins, etc. (hereinafter referred to as "fasteners").

[0003] Patent Document 1 describes an invention for preventing fluctuations in the time required to drive a fastener due to fluctuations in the plunger stopping position caused by a drop in battery voltage. Specifically, the invention describes a driving tool that controls the time the motor is energized based on the battery voltage.

[0004] Patent Document 2 describes a driving tool that can improve the positional accuracy of the plunger by determining the timing to stop the motor based on the time when the peak of the current flowing through the motor is detected. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-136656 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-30052 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of the driving tool described in Patent Document 1, the duration of time the motor is energized is set based solely on the battery voltage. Therefore, if the plunger moves at the same speed each time, it may be assumed that the plunger will stop in the same position. However, in reality, the plunger speed varies due to various factors, such as wear of parts, making it difficult to stabilize the plunger's stopping position.

[0007] Furthermore, in the case of the driving tool described in Patent Document 2, if the current peak cannot be detected, it becomes difficult to determine the timing to stop the motor. For example, if the plunger stops closer to the top dead center than the expected stopping position, increasing the starting load, and as a result, the current reaches its upper limit at startup, the current peak cannot be detected. As a result, it is impossible to determine the reference timing for the plunger stopping position.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a driving tool that makes it possible to stabilize the stopping position of the plunger. [Means for solving the problem]

[0009] A driving tool according to one aspect of the present disclosure includes a plunger, a motor for moving the plunger from bottom dead center to top dead center, a drive means for driving a fastener using the plunger by moving the plunger from top dead center to bottom dead center, a voltage fluctuation information acquisition means for acquiring voltage fluctuation information indicating the amount of fluctuation in voltage applied to the motor while the plunger is moving, and a control means for controlling the motor based on the voltage fluctuation information.

[0010] The voltage fluctuation information acquiring means may be configured to acquire voltage fluctuation information indicating an amount of fluctuation in voltage applied to the motor while the plunger is moving from the bottom dead center to the top dead center.

[0011] The voltage fluctuation information acquiring means may be configured to acquire voltage fluctuation information indicating an amount of fluctuation in voltage applied to the motor while the plunger is moving from the top dead center to the bottom dead center.

[0012] Here, the "amount of voltage fluctuation" is information indicating the amount of voltage fluctuation per unit time. The information indicating the amount of voltage fluctuation may be a differential value of the voltage.

[0013] Furthermore, in a driving tool in which a DC voltage is applied to the motor from a battery, the "voltage applied to the motor" may be the battery voltage.

[0014] The control means may be configured to control the motor based on the inflection point of the voltage.

[0015] Here, the "voltage inflection point" refers to the point at which the amount of change in the voltage per unit time changes from positive to negative or from negative to positive. The point at which the amount of change in the voltage per unit time changes from positive to negative or from negative to positive may be the point at which the second derivative of the voltage becomes zero or a point close to that point.

[0016] A driving tool according to another aspect of the present disclosure includes a plunger, a motor for moving the plunger from bottom dead center to top dead center, a drive means for driving a fastener using the plunger by moving the plunger from top dead center to bottom dead center, a current fluctuation information acquisition means for acquiring current fluctuation information indicating an amount of fluctuation in current flowing through the motor while the plunger is moving, and a control means for controlling the motor based on the current fluctuation information.

[0017] The current fluctuation information acquiring means may be configured to acquire current fluctuation information indicating the amount of fluctuation in current flowing through the motor while the plunger is moving from the bottom dead center to the top dead center.

[0018] The current fluctuation information acquiring means may be configured to acquire current fluctuation information indicating the amount of fluctuation in current flowing through the motor while the plunger is moving from the top dead center to the bottom dead center.

[0019] Here, the "amount of fluctuation in current" is information indicating the amount of fluctuation in current per unit time. The information indicating the amount of fluctuation in current may be a differential value of the current.

[0020] Furthermore, in a driving tool in which the plunger is driven by a three-phase brushless motor, the "current flowing through the motor" may be a winding current flowing through a winding of any one of the phases.

[0021] The control means may be configured to control the motor based on the inflection point of the current.

[0022] Here, the "current inflection point" refers to the point at which the fluctuation amount of the current per unit time changes from positive to negative or from negative to positive. The point at which the fluctuation amount of the current per unit time changes from positive to negative or from negative to positive may be the point at which the second derivative of the current becomes zero or a point close to that point.

[0023] Furthermore, the device may further include speed information acquisition means for acquiring speed information indicating the moving speed of the plunger after the plunger moves from the top dead center to the bottom dead center, and the control means may be configured to control the motor based on the speed information.

[0024] The speed information acquiring means may be configured to acquire speed information indicating a moving speed of the plunger while the plunger is moving from the bottom dead center to a standby position set between the bottom dead center and the top dead center.

[0025] Alternatively, the speed information acquiring means may be configured to acquire speed information indicating the moving speed of the plunger after the fastener is driven.

[0026] Additionally, the control means may be configured to initiate control to reduce the rotation speed of the motor based on the speed information.

[0027] Furthermore, one aspect of the present disclosure may further include a temperature information acquisition means for acquiring temperature information of the motor, and the control means may be configured to control the motor based on the temperature information.

[0028] Here, the control means may be configured to further start control to reduce the rotation speed of the motor based on the temperature information.

[0029] The vehicle may further include a battery for applying a voltage to the motor, and the voltage fluctuation information acquisition means may acquire, as the voltage fluctuation information, information indicating the amount of fluctuation in the power supply voltage of the battery.

[0030] A driving tool according to another aspect of the present disclosure includes a plunger, a motor for moving the plunger from bottom dead center to top dead center, a drive means for driving a fastener using the plunger by moving the plunger from top dead center to bottom dead center, a speed information acquisition means for acquiring speed information indicating the moving speed of the plunger after the plunger has moved from top dead center to bottom dead center, and a control means for controlling the motor based on the speed information.

[0031] A driving tool according to another aspect of the present disclosure includes a plunger, a motor for moving the plunger from bottom dead center to top dead center, a drive means for driving a fastener using the plunger by moving the plunger from top dead center to bottom dead center, a speed information acquisition means for acquiring speed information indicating the moving speed of the plunger after driving the fastener using the plunger, and a control means for controlling the motor based on the speed information.

[0032] The speed information acquiring means may be configured to acquire speed information indicating a moving speed of the plunger while the plunger is moving from the bottom dead center to a standby position set between the bottom dead center and the top dead center.

[0033] The control means may be further configured to initiate control to reduce the rotation speed of the motor based on the speed information.

[0034] A driving tool according to another aspect of the present disclosure is a driving tool comprising a plunger, a motor for moving the plunger from bottom dead center to top dead center, and a drive means for driving a fastener using the plunger by moving the plunger from top dead center to bottom dead center, and further comprising temperature information acquisition means for acquiring temperature information of electrical components mounted on the driving tool, and control means for controlling the motor based on the temperature information.

[0035] The electrical components include electronic devices mounted on the driving tool.

[0036] The electrical component may be the motor (including the stator winding).

[0037] The electrical component may be the control means, in particular a switching element of the control means.

[0038] The temperature information acquiring means may be attached in contact with or in close proximity to the electrical component so as to directly acquire the temperature of the electrical component, or may be attached at a distance from the electrical component so as to indirectly acquire the temperature of the electrical component. For example, the temperature information acquiring means may be provided on a printed wiring board on which an inverter circuit is mounted, or may be provided in the vicinity of the motor. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a front view of a driving tool according to one embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a driving tool according to one embodiment. [Figure 3] FIG. 3 is a perspective view of a plunger assembly according to one embodiment. [Figure 4] FIG. 4 is a cross-sectional view (front view) of a plunger assembly according to one embodiment. [Figure 5] FIG. 5 is a cross-sectional view (side view) of a plunger assembly according to one embodiment. [Figure 6] FIG. 6 is a cross-sectional view (plan view) of a plunger assembly according to one embodiment. [Figure 7] FIG. 7 is a perspective view including a plunger and a wire according to one embodiment. [Figure 8] FIG. 8 is a control block diagram of a driving tool according to one embodiment. [Figure 9] FIG. 9 shows an example of a waveform of the output voltage (power supply voltage) of a battery. [Figure 10] FIG. 10 is a timing chart showing an implantation method according to one embodiment. [Figure 11] FIG. 11 is a diagram showing the amount of voltage fluctuation when the plunger of the driving tool according to one embodiment reaches the top dead center. [Figure 12] FIG. 12 is a flowchart of an implantation method according to one embodiment. [Figure 13] FIG. 13 is a graph showing the output voltage of the battery and the winding current of the driving tool according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments.

[0041] [First embodiment] FIG. 1 shows a front view of an electric driving tool 10 according to a first embodiment (with a partial cross-section of the magazine), and FIG. 2 shows a cross-section of the driving tool 10 from the same direction (after all fasteners F in the magazine 14 have been ejected). The driving tool 10 is an electric nail gun configured to drive a plunger 32 (FIG. 2) using a motor (FIG. 2) to drive a nail (an example of a "fastener F"). Note that the terms "up and down," "front and back," and "left and right" in this specification refer to the orientation of the driving tool 10 shown in FIGS. 1 and 2. The leftward direction in FIGS. 1 and 2 corresponds to the direction in which the fastener F is ejected, and is therefore sometimes referred to as the ejection direction DR1 or ejection direction DR2. The opposite rightward direction in FIGS. 1 and 2 corresponds to the direction away from the ejection port 12A from which the fastener F is ejected, and is therefore sometimes referred to as the receding direction DR2. Directions may be expressed using directions X1, X2, Y, and Z shown in the drawings.

[0042] The driving tool 10 includes a housing 12, a magazine 14 that stores fasteners F to be driven by the driving tool 10, a driver 34 for driving out the fasteners F, a plunger 32 to which the driver 34 is attached, a motor 20 and a gear 22 for moving the plunger 32 from the bottom dead center to the top dead center, a coil spring 36 (an example of a "biasing member" or "driving means") that applies a driving force to move the plunger 32 from the top dead center to the bottom dead center, a moving member 38 disposed at the extending end of the coil spring 36, a wire 40 (an example of a "string-like member") that engages with the plunger 32 and the moving member 38 to link them, and a pulley 42 (an example of a "direction changing member") around which the wire 40 is hung. The driving tool 10 is further provided with a detachable battery B.

[0043] The driving tool 10 includes a housing 12 (hereinafter, the housing 12 and a portion fixed to the housing 12 may be referred to as the "tool body") that houses the main components of the driving tool 10, including the plunger 32. The housing 12 is provided with a grip portion 12B for an operator to hold, a bridge portion 12C that connects the motor 20 to a battery mounting portion to which a battery B is attached, and a nose portion 12D for driving out the fastener F. The grip portion 12B and the bridge portion 12C are each formed, for example, in a columnar shape extending in the vertical direction so that the operator can easily grasp them. The front end of the housing 12 (and the front end of the driving tool 10) is provided with the nose portion 12D, which has an ejection port 12A formed therein for ejecting the fastener F to the left of the drawing. A contact arm 12D1 may be attached to the tip of the nose portion 12D. The contact arm 12D1 is provided around the ejection port 12A so as to be able to protrude from the ejection port 12A, and functions as a safety device that allows the fastener F to be ejected only when the contact arm 12D1 is pressed against the object to be driven and the trigger 12E is pressed down.

[0044] A trigger 12E is provided on the housing 12. When pressed by a user, the trigger 12E establishes electrical continuity between the battery B and the motor 20. The trigger 12E is exposed on a surface of the grip portion 12B facing forward (the driving direction DR1 of the fastener F), and is biased forward (in the driving direction DR1) by a trigger biasing member 12F such as a spring.

[0045] The battery B is configured to be detachably attached to the lower end portions of the grip portion 12B and the bridge portion 12C. The battery B functions as a DC power source that supplies power to drive a motor and the like, and is configured to output a predetermined DC voltage (for example, 14 V to 20 V), such as a lithium-ion battery. The driving tool 10 can be portable and used by attaching the battery B. However, the battery B may be configured to be stored within the housing 12, or power may be supplied by means other than a battery.

[0046] Driving tool 10 includes magazine 14 attached below nose portion 12D. Magazine 14 is configured to be loaded with a plurality of linked fasteners F (FIG. 1). Magazine 14 includes pusher 14A that urges fasteners F toward nose portion 12D. Pusher 14A is urged by a urging member (not shown) so that when the leading fastener F is driven out by driver 34, adjacent fasteners F are supplied to the ejection path of nose portion 12D.

[0047] The driving tool 10 further includes a plunger assembly 30. FIG. 3 is a perspective view of the plunger assembly 30, and FIGS. 4 and 5 are cross-sectional views of the plunger assembly 30 with the coil spring 36 in a fully compressed state (an example of the "first state") and a fully extended state (an example of the "second state"), respectively (note that if FIG. 4 is a cross-sectional view of the front view, FIG. 5 corresponds to a cross-sectional view of the left side view). FIG. 6 is a cross-sectional view of the plunger assembly 30 in a plan view. FIG. 7 is a perspective view showing the plunger 32, a pin 38A that is part of the moving member 38, and a wire 40 that engages with the plunger 32 and the moving member 38. The plunger assembly 30 includes the driver 34, the plunger 32, the coil spring 36, the moving member 38, the wire 40, and the pulley 42, as well as a cylinder 44 that houses the coil spring 36 and a pair of guide rails 46 that regulate the movement direction of the plunger 32.

[0048] The driver 34 is a member that contacts and strikes the fastener F to drive it out. As shown in these drawings, the driver 34 according to this embodiment is made of a rigid metal body formed into a long, thin rod that extends in the driving direction DR1 of the fastener F. Because the fastener F is located on an extension line of the driver 34, when the driver 34 moves in the driving direction DR1, the front end of the driver 34 strikes the fastener F. The rear end of the driver 34 is connected to the plunger 32 and is configured to move integrally with the plunger 32.

[0049] The plunger 32 is a member that moves integrally with the driver 34 by moving from the top dead center to the bottom dead center to drive out the fastener F. As shown in FIG. 7 , the plunger 32 has four side walls: a first side wall 32A that engages with the wire 40; a second side wall 32B that connects to the first side wall 32A at a substantially right angle and engages with the guide rail 46; a third side wall 32C that connects to the second side wall 32B at a substantially right angle and is disposed substantially parallel to the first side wall 32A and engages with the driver 34; and a fourth side wall 32D that connects to the third side wall 32C and the first side wall 32A at a substantially right angle and is disposed substantially parallel to the second side wall 32B and engages with the guide rail 46. A cylinder 44, which will be described later, is disposed in a hollow area surrounded by the four side walls. The outer wall surface of the first sidewall 32A is provided with gear engagement portions 32A1, which are two protrusions provided at different heights. Engagement of the gear engagement portion 32A1 with a gear 22 (described later) causes the plunger 32 to move from the bottom dead center toward the top dead center against the elastic force (biasing force) of the coil spring 36. The top dead center of the plunger 32 is set in an area toward the rear end of the tool body, and the bottom dead center is set in an area between the top dead center and the nose portion 12D. Therefore, when the plunger 32 moves from the top dead center to the bottom dead center, the plunger 32 moves in a launch direction DR1 approaching the injection port 12A, and when the plunger 32 moves from the bottom dead center to the top dead center, the plunger 32 moves in a departure direction DR2 away from the injection port.

[0050] The first side wall 32A of the plunger 32 is further provided with a wire engaging portion 32A2. The wire engaging portion 32A2 includes a first portion 32A21 formed to protrude inward from the inner wall surface of the first side wall 32A (i.e., toward the third side wall 32C) and a second portion 32A22 extending from the end of the first portion 32A21 in a direction toward the top dead center. The surface of the first portion 32A21 facing the top dead center serves as a pressure-receiving surface for applying a force from the wire 40 to the plunger 32 in the launch direction DR1. The second portion 32A22 also restricts the wire 40 from shifting in a direction toward the third wall. Furthermore, by forming the first portion 32A21 to protrude in a direction toward the third side wall 32C, the wire 40 engaging with the pressure-receiving surface of the first portion 32A21 can extend along the inner wall surface of the first side wall 32A. This makes it possible to prevent the wire 40 from shifting in a direction away from the third side wall 32C. In addition, the wire engaging portion 32A2 is formed symmetrically with respect to an imaginary plane IP1 (FIG. 6) that is parallel to a plane that approximates the second side wall 32B and the fourth side wall 32D and is equidistant from both planes. This configuration makes it possible to prevent the plunger 32 from tilting due to an imbalance in the force acting on the plunger 32 from the wire 40.

[0051] The second side wall portion 32B and the fourth side wall portion 32D are formed symmetrically with respect to the imaginary plane IP1. The second side wall portion 32B and the fourth side wall portion 32D are provided with guide rollers 32B1 and 32D1, respectively, for engaging with the guide rail 46. Two guide rollers 32B1 and 32D1 are provided on each of the top dead center side and the bottom dead center side. Therefore, by engaging each of the two guide rollers 32B1 and 32D1 with the guide rail 46, it is possible to prevent the plunger 32 from tilting during movement.

[0052] The third side wall portion 32C is provided with a driver engaging portion 32C1 that is formed symmetrically with respect to the imaginary plane IP1 and to which the rear end of the driver 34 is connected. This makes it possible to prevent the plunger 32 from tilting due to the reaction force that the plunger 32 receives when the driver 34 strikes the fastener F.

[0053] As shown in these drawings, the plunger 32 is configured so that, when the direction of movement of the plunger 32 (the direction connecting the top dead center and the bottom dead center) is used as the reference, the distance between the driver engagement portion 32C1 and the injection port 12A is smaller than the distance between the wire engagement portion 32A2 and the injection port 12A.

[0054] The cylinder 44 is a member that houses the coil spring 36 and guides the movement direction of the pin 38A that forms part of the moving member 38. The cylinder 44 according to this embodiment includes a cylindrical portion 44A formed in a cylindrical shape and a cap portion 44C that corresponds to a lid for the cylindrical portion 44A. The cylinder 44 penetrates a hollow area surrounded by the four side wall portions of the plunger 32 and is fixed to the housing 12 so that the movement direction of the plunger 32 and the central axis of the cylinder 44 are approximately parallel, and the cap portion 44C fixes the guide rail 46.

[0055] A coil spring 36, which is a compression spring that can expand and contract in the direction of the central axis of the cylinder 44, i.e., in the direction of movement of the plunger 32, is housed inside the cylinder 44. One end 36A of the coil spring 36 is fixed to the bottom surface of the cylinder on the injection port side (the bottom dead center side of the plunger 32). A moving member 38 is disposed at the other end 36B of the coil spring 36, and tension is applied to the moving member 38 on the one end 36A side of the coil spring 36 by a wire 40. Therefore, both the other end 36B of the coil spring and the moving member 38 are configured to be movable. When the coil spring 36 compresses from an extended state, the other end 36B of the coil spring and the moving member 38 move in the ejection direction DR1. When the coil spring 36 expands from a compressed state to its original state, the other end 36B of the coil spring and the moving member 38 move in the moving direction DR2 away from the injection port 12A. A pair of holes 44B are formed in the wall of the cylinder 44, extending parallel to the central axis, that is, parallel to the direction in which the coil spring 36 extends.

[0056] The moving member 38 directly or indirectly engages with a portion of the wire 40, thereby moving the wire 40 as the other end 36B of the coil spring expands. The moving member 38 according to this embodiment includes an annular portion 38B disposed at the other end 36B of the coil spring, and a pin 38A fixed to the annular portion 38B and with which both ends of the wire 40 are engaged. In this embodiment, a pair of holes 44B formed in the wall of the cylinder 44 are parallel to two planes that approximate the first side wall portion 32A and the third side wall portion 32C of the plunger 32 and are formed so as to intersect with an imaginary plane IP2 ( FIG. 6 ) that passes through the central axes of the cylinder 44 and the coil spring 36. Furthermore, both ends of the pin 38A engage with the pair of holes 44B so that the extending direction of the pin 38A is approximately parallel to this imaginary plane. Therefore, even if the moving member 38 including the pin 38A moves in the central axis direction of the cylinder 44 as the coil spring 36 expands or compresses, it is possible to prevent the pin 38A from twisting in the circumferential direction of the cylinder 44.

[0057] The wire 40 is attached to the moving member 38 and the plunger 32 to move the moving member 38 and the plunger 32 in conjunction with each other. In this embodiment, the wire 40 is formed into a ring shape by connecting one end of the wire 40 to a portion spaced from the end of the wire 40. The pin 38A engages with the wire 40 by passing through this ring-shaped portion. The wire 40 engaging with the pin 38A passes through a hole in the annular portion 38B of the moving member 38 and extends in the thrust direction DR1 along the central axis of the coil spring 36. After passing through a hole formed in the bottom surface of the cylinder 44, the wire 40 is wound around the pulley 42, whereby it changes direction, extends in the separation direction DR2, and engages with the pressure-receiving surface of the wire engagement portion 32A2 of the plunger 32. The wire 40 then extends in the thrust direction DR1, changes direction by being wound around the pulley 42, and extends in the separation direction DR2 along the central axis of the coil spring 36. At the other end of the wire 40, the other end of the wire 40 is connected to a portion spaced from the end of the wire 40 to form a loop, and the pin 38A is passed through this loop-shaped portion to engage with the wire 40. Therefore, both ends of the wire 40 are engaged with the pin 38A, and the middle portion of the wire 40 is engaged with the plunger 32.

[0058] That is, the wire 40 comprises a first portion 40A including one end that engages with the moving member 38, a second portion 40B that is connected to the first portion 40A and includes a portion that extends in the launch direction DR1, a third portion 40C that is connected to the second portion 40B and includes a portion that extends approximately in the moving away direction, a fourth portion 40D that is connected to the third portion 40C and engages with the plunger 32, a fifth portion 40E that is connected to the fourth portion 40D and includes a portion that extends approximately in the launch direction DR1, a sixth portion 40F that is connected to the fifth portion 40E and includes a portion that extends in the moving away direction DR2, and a seventh portion 40G that is connected to the sixth portion 40F and includes the other end that engages with the moving member 38.

[0059] The drive mechanism for moving the plunger 32 from the bottom dead center to the top dead center is composed of a motor 20 and a gear 22. The motor 20 according to this embodiment shown in FIG. 2 is composed of a three-phase DC brushless motor, and is disposed, for example, within the bridge portion 12C so that the output shaft of the motor 20 is substantially perpendicular to the driving direction DR1 and the receding direction DR2. A gear having the output shaft of the motor 20 as its rotation axis meshes with a first gear 22A constituting the gear 22, and the first gear 22A meshes with a second gear 22B constituting the gear 22. The first gear 22A is disposed in the receding direction DR2 relative to the gear of the output shaft of the motor 20, and the second gear 22B is disposed in the receding direction DR2 relative to the first gear 22A. The first gear 22A and the second gear 22B are provided with torque rollers (not shown) that are parallel to the rotation axis and protrude toward the outer wall surface of the first side wall portion 32A of the plunger 32. The torque roller rotates about the central axis of the first gear 22A (second gear 22B) as the first gear 22A (second gear 22B) rotates. Because the central axis of the first gear 22A (second gear 22B) is parallel to the output shaft of the motor 20, the torque roller reciprocates in the thrust direction DR1 and the separation direction DR2 as the first gear 22A (second gear 22B) rotates. When the plunger 32 is near the bottom dead center, the torque roller of the first gear 22A engages with one of the convex portions provided on the bottom dead center side as the gear engagement portion 32A1. Then, as the first gear 22A rotates, the torque roller moves in the separation direction DR2, pushing up the gear engagement portion 32A1 of the plunger 32 in the separation direction DR2, thereby enabling the plunger 32 to move in the separation direction DR2. When the torque roller of the first gear 22A moves to the farthest position in the separating direction DR2, the torque roller of the second gear 22B engages with the other convex portion provided on the top dead center side as the gear engagement portion 32A1. As the second gear 22B rotates, the torque roller moves in the separating direction DR2, pushing the gear engagement portion 32A1 of the plunger 32 further in the separating direction DR2, thereby enabling the plunger 32 to move further in the separating direction DR2. When the torque roller of the second gear 22B moves to the farthest position in the separating direction DR2, the plunger 32 reaches the top dead center, and the engagement between the gear engagement portion 32A1 and the second gear 22B is released.

[0060] The driving tool 10 further includes a control unit 50 for driving the motor 20. The control unit 50 is mounted on a PCB board 24 (FIG. 2) disposed in the gap between the motor 20 and the battery B inside the bridge portion 12C.

[0061] FIG. 8 shows a control block diagram of the driving tool 10. The motor 20 to be controlled includes a rotor and a stator having three-phase windings (an example of a "stator winding"). The motor 20 is configured to be able to rotate the rotor having a permanent magnet by passing a three-phase alternating current through the three-phase windings to generate a rotating magnetic field. The motor 20 is not provided with a position detection sensor, such as a Hall IC, for detecting the position of the rotor of the motor 20. However, the motor 20 may be provided with a position detection sensor for detecting the position of the rotor.

[0062] The control unit 50 includes an inverter circuit 50A for applying voltage to the three-phase windings of the motor 20, a CPU 50B for generating a control signal for switching the inverter circuit 50A and supplying it to the inverter circuit 50A, a voltage detection circuit 50C for detecting the voltage of battery B, and a power supply circuit 50D for supplying power output from battery B to each active component such as the CPU 50B.

[0063] The inverter circuit 50A is configured with, for example, six switching elements, each made of, for example, FETs (Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors), connected in a three-phase bridge configuration between a positive bus (power supply line) and a negative bus (ground line) connected to the output terminals of the battery B, and freewheel diodes connected in parallel to each of these switching elements. The three output terminals of this inverter circuit are connected to the three-phase windings of the motor 20, respectively.

[0064] The CPU 50B is composed of hardware including a non-volatile semiconductor memory (e.g., flash memory) that stores computer programs for executing the arithmetic processing described in this embodiment, such as the control program for the motor 20, volatile semiconductor memory (SRAM and DRAM) that temporarily stores data such as the results of the arithmetic processing, a processor that executes the computer program read from the semiconductor memory and generates control signals for controlling the inverter circuit 50A, and a driver circuit that generates PWM (pulse width modulated) drive signals (PWM signals) that are supplied to the bases (or gates) of each switching element of the inverter circuit 50A based on the control signals generated by the processor.

[0065] The CPU 50B includes a voltage information acquisition unit 50B1 that acquires voltage information indicating the voltage applied to the motor 20 from the voltage detection circuit 50C; a voltage fluctuation information acquisition unit 50B2 that acquires information indicating the amount of change in voltage per unit time based on the voltage information acquired by the voltage information acquisition unit 50B1; an inflection point detection unit 50B3 that detects an inflection point (maximum point) of the amount of change in voltage per unit time at which the amount of change in voltage per unit time changes from positive to negative based on the voltage fluctuation information acquired by the voltage fluctuation information acquisition unit 50B2; a rotational speed acquisition unit 50B4 that acquires information indicating the rotational speed of the motor 20; and a brake control time determination unit 50B5 that sets the time from the detection of the inflection point to the start of brake control of the motor 20 (hereinafter referred to as the "brake start timing") based on the rotational speed of the motor 20 at the time the inflection point is detected by the inflection point detection unit 50B3.

[0066] The voltage information acquisition unit 50B1 acquires information indicating the voltage applied to the motor 20 from the voltage detection circuit 50C. The inventors of the present application focused on the fact that the voltage applied to the motor 20 fluctuates during one cycle of operation of the driving tool 10 and came up with the idea of ​​estimating the position of the plunger 32 based on the voltage fluctuation information and controlling the motor 20 based on this. However, they noticed that the signal acquired from the voltage detection circuit 50C fluctuates slightly due to ripples generated each time the switching elements of the inverter circuit 50A switch. FIG. 9 shows the original waveform of the output voltage (power supply voltage) of battery B acquired from the voltage detection circuit 50C and an enlarged view of the original waveform (although the scale of the enlarged view has been changed for convenience). The voltage information acquisition unit 50B1 is configured to acquire the voltage of battery B with reduced ripple effects by sampling the signal value acquired from the voltage detection circuit 50C immediately before the switching elements of the inverter circuit 50A switch. FIG. 10(E) shows the voltage of battery B obtained by sampling the signal value immediately before switching is performed and connecting adjacent signal values.

[0067] The voltage fluctuation information acquiring unit 50B2 acquires voltage fluctuation information based on voltage information sampled by the voltage information acquiring unit 50B1 at a predetermined cycle (e.g., every 3 ms to 6 ms). Specifically, the voltage fluctuation information acquiring unit 50B2 acquires information corresponding to the differential value of the voltage by acquiring the difference between the voltage information sampled immediately before and the voltage information sampled immediately before. However, to reduce the influence of noise, the voltage fluctuation information acquiring unit 50B2 may be configured to acquire voltage fluctuation information based on voltage information obtained by averaging multiple samples.

[0068] The inflection point detection unit 50B3 detects an inflection point (a maximum point of the voltage fluctuation amount) where the fluctuation amount of the voltage fluctuation amount changes from positive to negative based on the voltage fluctuation information acquired by the voltage fluctuation information acquisition unit 50B2. Specifically, the inflection point detection unit 50B3 determines whether the fluctuation amount of the voltage fluctuation amount is equal to or greater than 0 based on the voltage fluctuation information acquired by the voltage fluctuation information acquisition unit 50B2, and detects the inflection point by detecting that the fluctuation amount of the voltage fluctuation amount is not equal to or greater than 0 (i.e., negative). However, in order to reduce the influence of noise, etc., the inflection point may be detected by continuously detecting that the fluctuation amount of the voltage fluctuation amount is not equal to or greater than 0.

[0069] As will be described later, the inflection point (maximum point of voltage fluctuation) at which the voltage fluctuation amount changes from positive to negative is observed when the plunger 32 reaches the top dead center. Therefore, by detecting the inflection point of the voltage fluctuation amount, it is possible to estimate that the plunger 32 is near the top dead center. Therefore, by controlling the motor 20 based on the detection of the inflection point at which the voltage fluctuation amount changes from positive to negative, it is possible to stabilize the stop position of the plunger 32.

[0070] The rotational speed acquisition unit 50B4 acquires information indicating the number of rotations per hour (rotational speed) of the rotor of the motor 20. The rotational speed acquisition unit 50B4 acquires the rotational speed based on, for example, the phase voltage of the motor 20. More specifically, the rotational speed acquisition unit 50B4 acquires information indicating the zero-crossing points at which the back electromotive force generated in a non-energized phase becomes equal to the midpoint potential of the voltage of the battery B, and acquires the interval between the zero-crossing points, thereby acquiring information indicating the rotational speed of the rotor of the motor 20. The zero-crossing points may be detected for the phase voltage of one of the three-phase windings, or may be detected for the phase voltages of two or all of the phase windings. Instead of acquiring the rotational speed based on the phase voltages, the information indicating the rotational speed may be acquired using a position detection sensor such as a Hall IC.

[0071] The brake control time determination unit 50B5 determines the brake start timing from the time of detecting the inflection point until the start of brake control of the motor 20 based on the rotational speed of the motor 20 when the inflection point is detected by the inflection point detection unit 50B3. When the inflection point is detected, it is estimated that the plunger 32 is near the top dead center. Therefore, it is possible to set the time until the brake control of the motor 20 is started, taking into account the time required for the plunger 32 to reach the bottom dead center from the top dead center. Here, the brake control time determination unit 50B5 may be further configured to change the brake start timing based on the rotational speed of the motor 20 when the inflection point detection unit 50B3 detects the inflection point. For example, if the rotational speed of the motor 20 is high, it is considered that the time until the standby position is reached will be shorter than when the rotational speed is low. Therefore, it is possible to set the brake start timing shorter than usual and control the motor 20 to brake earlier. On the other hand, when the rotation speed of motor 20 is low, it is considered that the time to reach the standby position will be longer than when the rotation speed is not low. Therefore, it is possible to set the braking start timing longer than usual and control motor 20 so that the brake is applied later.

[0072] By adopting such a configuration, it is possible to control the position of the plunger 32 while suppressing the influence of variations due to changes over time such as wear of parts, the remaining capacity of the battery B, and the like.

[0073] The voltage detection circuit 50C acquires voltage information indicating the voltage applied to the motor 20 and supplies it to the CPU 50B. Specifically, the voltage detection circuit 50C is configured to include a plurality of resistance elements connected in series to a positive bus connected to the output terminal of the battery B, and to supply a divided voltage value to the CPU 50B. Compared to the current detection circuits of other embodiments, the voltage detection circuit can be configured from a plurality of resistance elements and does not require an active element, which is advantageous in terms of cost.

[0074] The power supply circuit 50D supplies the power output from the battery B to each active component such as the CPU 50B.

[0075] A driving method using the driving tool 10 according to this embodiment will be described below. Fig. 10 is a timing chart showing the driving method using the driving tool 10.

[0076] In Figure 10, the horizontal axis represents time. Figure 10(A) shows the contact SW signal, which indicates whether or not the contact arm 12D1 is in contact with the object into which the fastener F is driven. At time t0, when the contact arm 12D1 comes into contact with the object, the contact SW signal turns ON. The CPU 50B receives the contact SW signal and detects that the contact arm 12D1 is in contact with the object. Thereafter, the contact SW signal remains ON as long as the contact arm 12D1 is in contact with the object.

[0077] 10(B) shows the trigger SW signal indicating whether or not the trigger 12E is pressed. At time t1, when the operator presses the trigger 12E, the trigger SW signal turns ON. The CPU 50B receives the trigger SW signal and detects that the trigger 12E is pressed. Thereafter, the trigger SW signal remains ON as long as the trigger 12E is pressed.

[0078] FIG. 10(C) shows the state of the motor 20. At time t1, when both the trigger SW signal and the contact SW signal are turned ON, the CPU 50B supplies a PWM signal to the inverter circuit 50A to drive the motor 20. Each switching element of the inverter circuit 50A performs a switching operation based on the PWM signal from the CPU 50B. When the switching elements are turned ON, the output voltage of battery B is applied to the three-phase windings that make up the stator of the motor 20, causing a winding current to flow through the windings of each phase. The rotor of the motor 20 begins to rotate in accordance with the rotating magnetic field generated by the three-phase windings.

[0079] 10(D) shows the position of the plunger 32. In an initial state before time t1, the plunger 32 is stationary at a standby position midway between the top dead center and the bottom dead center. When the motor 20 starts to drive at time t1, the torque roller provided on the second gear 22B comes into contact with the gear engagement portion 32A1 of the plunger 32 and pushes the plunger 32 upward in the separation direction DR2. Because the plunger 32 is connected to the moving member 38 by the wire 40, in conjunction with the movement of the plunger 32 in the separation direction DR2, the moving member 38 moves in the firing direction DR1 while compressing the coil spring 36.

[0080] While the plunger 32 moves from the top dead center to the bottom dead center, the voltage information acquisition unit 50B1 of the CPU 50B acquires information indicating the voltage applied to the motor 20, the voltage fluctuation information acquisition unit 50B2 acquires voltage fluctuation information, and the inflection point detection unit 50B3 periodically determines whether the fluctuation amount of the voltage fluctuation is greater than or equal to 0.

[0081] FIG. 10(E) shows the voltage of battery B (corresponding to information indicating the voltage applied to motor 20) acquired by voltage information acquisition unit 50B1 of CPU 50B. FIG. 10(F) shows the amount of fluctuation in the voltage of battery B (corresponding to voltage fluctuation information indicating the amount of fluctuation in the voltage applied to motor 20) acquired by voltage fluctuation information acquisition unit 50B2 of CPU 50B. The amount of fluctuation in the voltage of battery B approximates the differential value of battery B by increasing the sampling frequency. FIG. 10(G) shows the amount of fluctuation in the amount of fluctuation in the voltage of battery B. The amount of fluctuation in the amount of fluctuation in the voltage of battery B approximates the second differential value of battery B by increasing the sampling frequency.

[0082] As shown in FIG. 10(E), the voltage applied to the motor 20 fluctuates during one cycle of operation of the driving tool 10. When the motor 20 starts to drive at time t1, a winding current flows, causing the output voltage of battery B to drop. When the winding current reaches its upper limit due to a large starting load, the output voltage remains lowered as shown in the figure. The amount of drop in the output voltage of battery B depends on the specifications of the driving tool 10, and is, for example, 3V to 8V.

[0083] Thereafter, when the winding current falls below the upper limit, the output voltage of battery B increases. However, as shown after time t2, as the plunger 32 approaches top dead center, the coil spring 36 compresses, and the biasing force of the coil spring 36 increases. The winding current increases to move the plunger 32 toward top dead center against this biasing force. As a result, the output voltage of battery B begins to decrease. At this time, the amount of fluctuation in the voltage of battery B may have a negative value, as shown in FIG. 10(F).

[0084] At time t3, the plunger 32 reaches the top dead center. At this time, the engagement between the plunger 32 and the gear 22 is released. As a result, the coil spring 36, which was in a compressed state, expands all at once. The moving member 38 moves together with the other end of the coil spring 36 in the separation direction DR2, which corresponds to the expansion direction of the coil spring 36. Because the moving member 38 is connected to the plunger 32 by the wire 40, the plunger 32 and the driver 34 move in the launch direction DR1 in conjunction with the movement of the moving member 38 in the separation direction DR2.

[0085] FIG. 11 is an enlarged view of the voltage of Battery B and the amount of change in the voltage of Battery B when the plunger 32 reaches the top dead center at time t3. As shown in the figure, when the plunger 32 reaches the top dead center, the biasing force of the coil spring 36 is released and the load of the motor 20 is suddenly reduced. This causes a sudden decrease in the motor current and a momentary sharp increase in the output voltage of Battery B, followed by a gradual increase in the output voltage of Battery B. Therefore, based on the plunger 32 reaching the top dead center, the derivative of the output voltage of Battery B reaches a local maximum at time t4. At time t5, the inflection point detection unit 50B3 detects an inflection point in the battery voltage based on this local maximum. In order for the inflection point detection unit 50B3 to detect the inflection point, it must detect that the second-order derivative of the output voltage of Battery B (the amount of change in the voltage fluctuation) is negative. Therefore, a time lag occurs between time t4 and time t5. Therefore, in this embodiment, the inflection point detection unit 50B3 is configured to detect the maximum point when the plunger 32 reaches the bottom dead center and moves from the bottom dead center to the top dead center (or when the plunger 32 moves from the bottom dead center to the standby position).

[0086] At time t5, rotation speed acquisition unit 50B4 acquires information indicating the number of rotations per hour (rotation speed) of the rotor of motor 20 when inflection point detection unit 50B3 detected the inflection point.

[0087] Also at time t5, the brake control time determination unit 50B5 determines the brake start timing based on the rotation speed of the motor 20 acquired from the rotation speed acquisition unit 50B4. Specifically, a lookup table for determining the brake start timing based on the rotation speed may be stored in the nonvolatile semiconductor memory of the CPU 50B.

[0088] Similarly, at time t5, when the brake control time determination unit 50B5 determines the braking start timing, the counter of the CPU 50B starts counting up (FIG. 10(H)).

[0089] While the plunger 32 is moving from the top dead center to the bottom dead center, the CPU 50B supplies a control signal to the inverter circuit 50A to rotate the rotor of the motor 20, so that the rotor of the motor 20 continues to rotate. Because the force impeding the rotation of the motor 20 is released, the rotation speed of the rotor of the motor 20 may increase. When the plunger 32 reaches near the bottom dead center (or just before reaching that point), the driver 34, which moves in the ejection direction DR1 together with the plunger 32, ejects the fastener F supplied to the nose portion 12D in the ejection direction DR1. The fastener F is ejected from the injection nozzle 12A.

[0090] When the plunger 32 reaches the bottom dead center, the first gear 22A, which rotates in synchronization with the rotor of the motor 20, is configured to engage with the gear engagement portion 32A1 of the plunger 32. As a result, the plunger 32 starts to move from the bottom dead center toward the top dead center. As the plunger 32 moves toward the top dead center, the coil spring 36 is compressed.

[0091] At time t6, when the count of the CPU 50B reaches a predetermined value, the CPU 50B starts deceleration control, for example, brake control as an example of deceleration control, to decelerate the rotation of the motor 20. Specifically, the CPU 50B generates a PWM signal with a smaller duty ratio than during normal rotation, and outputs it to each switching element of the inverter circuit 50A.

[0092] The deceleration control by CPU 50B significantly reduces the rotation speed of the rotor of motor 20. At this time, regenerative power is generated as motor 20 decelerates, and the voltage of battery B further increases as shown in FIG.

[0093] As shown in FIG. 10(D), even if the rotation speed decreases, the motor 20 continues to rotate, and the plunger 32 continues to move gently toward the top dead center.

[0094] Various methods can be used for deceleration control to reduce the rotational speed of the rotor of the motor 20. For example, a short-circuit brake may be used, in which the power supply to the upper arm of the inverter circuit is cut off and only the power supply to the lower arm is supplied. In this case, the braking force is high, but the amount of heat generated by the motor is large. Also, regenerative braking cannot be used.

[0095] Alternatively, a PWM signal may be generated to turn off the power supply to the upper arm of the inverter circuit and power only the lower arm, thereby applying chopper control (chopper braking) to the short-circuit brake. In this case, the braking force is lower than with short-circuit braking, but it is possible to suppress the amount of heat generated by the motor. It also becomes possible to use regenerative braking.

[0096] Furthermore, an open brake may be used, which cuts off the power supply to the upper and lower arms of the inverter circuit. In this case, the braking force is significantly reduced, but the amount of heat generated by the motor can also be significantly reduced. Also, regenerative braking cannot be used.

[0097] Thereafter, at time t7, the rotor of motor 20 stops rotating. The timing at which motor 20 stops rotating can be set as appropriate. For example, a control signal pattern for brake control may be prepared such that motor 20 stops when CPU 50B outputs a control signal according to a predetermined pattern to inverter circuit 50A.

[0098] FIG. 12 is a flowchart showing the process for controlling the stop position of the plunger 32, which is one of the above-described series of processes.

[0099] In step S10, the CPU 50B starts a process for detecting the reference position. Note that the process for detecting the reference position does not necessarily have to start at time t1, which is the start time of driving the motor 20. For example, the process for detecting the reference position may be executed using a counter after a predetermined time has elapsed after driving the motor 20 has started (for example, at a timing before the plunger 32 reaches the top dead center).

[0100] Next, the voltage information acquisition unit 50B1 of the CPU 50B acquires voltage information of the battery B (step S11), and the voltage fluctuation information acquisition unit 50B2 acquires voltage fluctuation information of the battery B based on the acquired voltage information (step S12).

[0101] The inflection point detection unit 50B3 of the CPU 50B determines whether the voltage fluctuation amount is a maximum point (step S13). Specifically, it determines whether the fluctuation amount of the voltage fluctuation amount is equal to or greater than 0 based on the voltage fluctuation information acquired by the voltage fluctuation information acquisition unit 50B2. If it is not a maximum point (NO), step S11 and subsequent steps are periodically repeated. Note that various logic for determining a maximum point can be set. For example, it may be determined that a maximum point has been reached when the voltage fluctuation amount is positive for two consecutive times and then negative for the following two consecutive times.

[0102] If it is the maximum point (YES), the CPU 50B determines that the top dead center has been detected as the reference position of the plunger 32 (step S14).

[0103] The rotational speed acquisition unit 50B4 of the CPU 50B acquires rotational speed information of the motor 20 when the top dead center is detected (step S15), and the brake control time determination unit 50B5 determines the braking start timing based on the rotational speed of the motor 20 (step S16). For example, if the rotor rotational speed acquired in step S15 is high, the threshold is set small to advance the braking start timing, and if the rotor rotational speed is low, the threshold is set large to delay the braking start timing. Even when performing the same driving operation, the speed of the plunger 32 and the rotational speed of the rotor of the motor 20 may vary depending on the aging of the components of the driving tool 10. Therefore, the driving tool 10 is configured to acquire the rotational speed of the rotor of the motor 20 and control the motor 20 based on this. The rotor rotational speed used by the CPU 50B for control is the rotor rotational speed after the plunger 32 reaches the bottom dead center. Since the rotational speed of the rotor of the motor 20 increases after the plunger 32 reaches bottom dead center, which results in greater variation in the rotational speed of the rotor, controlling the motor 20 based on information indicating the rotational speed of the rotor after the plunger 32 reaches bottom dead center makes it possible to more stabilize the stopping position of the plunger 32. Note that the logic for determining the braking start timing, which serves as the reference for starting deceleration control based on the rotational speed, can be designed as appropriate depending on the configuration of the actual driving tool.

[0104] Furthermore, the CPU 50B determines whether or not the count value that started to be counted up in step S17 has reached or exceeded a threshold value that was set based on the braking start timing (step S18).

[0105] If it is determined in step S18 that the count value is equal to or greater than the threshold value (YES), the CPU 50B starts deceleration control (e.g., brake control) to decelerate the rotation of the motor 20 (step S19). An example of the brake control method has been described above, so a description thereof will be omitted.

[0106] If it is not determined in step S18 that the count value is equal to or greater than the threshold value (NO), step S18 is periodically re-executed.

[0107] When the CPU 50B completes the brake control, the control unit 50 including the CPU 50B ends the control of the motor 20 (step S20). At this time, the rotor of the motor 20 stops rotating. Also, the plunger 32 stops at the stop position (standby position).

[0108] When fasteners are driven continuously, the operations from time t1 onwards in FIG. 10 are repeated.

[0109] In the driving tool 10 described above, the control unit 50 is configured to control the motor 20 based on the amount of fluctuation in the voltage applied to the motor 20. This makes it possible to stabilize the stopping position of the plunger even when the absolute value of the rotational speed varies due to a drop in battery voltage, deterioration of components over time, etc. This makes it possible to reduce the variation in the response time from the stopping position to the execution of driving.

[0110] Furthermore, it is possible to eliminate the need for a sensor (typically a microswitch) for detecting top dead center. Because high dust-proof and waterproof performance is required for driving tools, the microswitch must be installed appropriately, taking into consideration the intrusion of dust, machine oil, and water from the outside. However, as the mechanical contacts of the microswitch wear due to the impact of driving, problems arise, such as chattering and the sensor being unable to properly detect top dead center. While providing a filter circuit is one way to prevent chattering, filtering creates a time lag before the signal is confirmed. The driving tool 10 according to this embodiment makes it possible to control the motor without using a microswitch. However, a modification may be made in which a microswitch is installed and the motor and plunger position are controlled in conjunction with information obtained from the microswitch.

[0111] Similarly, it is possible to eliminate the need for Hall ICs. Since Hall ICs, like microswitches, are required to have dustproof and waterproof properties, installing a Hall IC leads to an increase in the size and cost of the driving device. According to the driving tool 10 of this embodiment, it is possible to control the motor without using a Hall IC. However, a modification may be made in which a Hall IC is installed, information indicating the amount of fluctuation in rotation speed is acquired based on information from the Hall IC, and the motor and plunger positions are controlled based on this information.

[0112] Although the control unit 50 detects the maximum point of the voltage fluctuation as information indicating the amount of voltage fluctuation and uses this information to control the motor 20, this is not limiting. For example, it may detect when the amount of voltage fluctuation exceeds a threshold and use this information to control the motor. Even in this embodiment, it is possible to reduce the effects of variations in the absolute value of the voltage due to battery consumption, etc. Alternatively, other inflection points of the voltage fluctuation may be detected and used to control the motor. Furthermore, it is also possible to prepare an expected voltage fluctuation waveform in advance and compare it with the actual voltage fluctuation waveform to control the motor based on this. However, since the maximum point of the voltage fluctuation is a characteristic that occurs when the plunger moves from top dead center to bottom dead center, detecting the maximum point facilitates stable position control of the plunger.

[0113] Furthermore, the inventors of this application focused on the fact that even if the amount of voltage fluctuation is the same, the absolute value of the motor's rotational speed may differ, and adopted a configuration that controls the plunger position based on the rotational speed. For example, wear on the main parts of the driving tool may cause the rotor's rotational speed to differ even at the same timing. Therefore, the plunger position is controlled based on the motor's rotational speed in addition to the amount of voltage fluctuation. This configuration makes it possible to control the plunger's stopping position more accurately.

[0114] For example, if the absolute value of the motor rotation speed is large, executing normal brake control may cause the plunger to stop closer to the top dead center than expected. On the other hand, if the absolute value of the motor rotation speed is small, executing normal brake control may cause the plunger to stop closer to the bottom dead center than expected. Therefore, by controlling the motor based on the rotor rotation speed at a specified timing, it is possible to suppress variation in the plunger stopping position due to variation in the rotor rotation speed.

[0115] Furthermore, the driving tool 10 according to the present embodiment acquires information indicating the rotation speed of the motor based on the phase voltage, but may also be configured to acquire information indicating the rotation speed of the motor based on, for example, the phase current.

[0116] Furthermore, while the driving tool 10 uses a counter as a means for determining the braking start timing, the present invention is not limited to this. For example, the amount of rotation (number of rotations) of the motor 20 may be measured and the braking start timing may be determined based on this. For example, the driving tool may be configured so that the braking start timing is determined when the motor 20 has rotated 20 times since the top dead center was detected. The means for measuring the amount of rotation of the motor 20 may, for example, use the rotation speed acquisition unit 50B4 to measure the amount of rotation based on a change in phase voltage, or may use a Hall IC or the like to measure the amount of rotation.

[0117] Various techniques can be used to move the plunger using a gear or the like driven by a motor, and disengage the gear or the plunger at the top dead center to move the plunger toward the bottom dead center. For example, the techniques described in Patent Documents 1 and 2 may be employed.

[0118] Furthermore, the present invention can be modified in various ways within the scope of ordinary creativity of those skilled in the art. For example, the present invention can be applied to a driving tool for driving fasteners other than nails.

[0119] [Second embodiment] Hereinafter, a driving tool according to the second embodiment will be described. Components having the same or similar functions as those in the other embodiments will be given the same names and descriptions thereof will be omitted.

[0120] The driving tool 10 according to the first embodiment has a configuration for controlling the motor 20 by determining the timing for starting braking based on voltage fluctuation information and rotational speed information of the motor 20.

[0121] The driving tool according to this embodiment is configured to control the motor by determining a control pattern for deceleration control based on voltage fluctuation information and motor rotational speed information. The period during which such a control pattern is used may be a fixed period or a variable period. As an example, the driving tool according to this embodiment is configured to control the motor by selecting a control pattern with different duty ratios of the PWM signal based on the voltage fluctuation information and motor rotational speed information. More specifically, based on the voltage fluctuation information and the motor rotational speed information, the driving tool is configured to supply a control signal to the motor inverter circuit when the motor rotational speed is at a first rotational speed, with a brake duty for decelerating the motor that is greater than the brake duty when the motor rotational speed is at a second rotational speed that is lower than the first rotational speed.

[0122] Even with such a driving tool, the plunger position is controlled based on voltage fluctuation information, so that the standby position of the plunger can be stabilized.

[0123] [Third embodiment] Hereinafter, a driving tool according to the third embodiment will be described. Components having the same or similar functions as those in the other embodiments will be given the same names and descriptions thereof will be omitted.

[0124] The driving tool 10 according to the first embodiment has a configuration for controlling the motor 20 based on voltage fluctuation information. The driving tool according to the present embodiment has a configuration for controlling the motor by determining a control pattern for deceleration control based on current fluctuation information and motor rotation speed information.

[0125] 13 is a graph showing the output voltage of battery B and the winding current during one cycle of the driving tool, which includes times t0 to t7. As shown in this graph, the inventors of the present application have noticed that there is a correlation between the output voltage of battery B and the winding current. In particular, the inventors of the present application have noticed that the envelope A1 of the output voltage of battery B and the envelope A2 of the winding current have symmetrical shapes.

[0126] Therefore, the driving tool according to this embodiment includes a current fluctuation information acquisition unit for acquiring current fluctuation information indicating the amount of fluctuation in the current flowing through the motor 20 while the plunger 32 is moving, and is configured to control the motor 20 based on the current fluctuation information. The driving tool may further be configured to detect a minimum point of the current fluctuation based on the current fluctuation information and control the motor 20 based on the detection of the minimum point. When the plunger 32 reaches the top dead center, the load suddenly decreases, and therefore the current fluctuation has a minimum point. Therefore, by detecting the minimum point of the current fluctuation, it is possible to estimate that the plunger 32 has reached the top dead center.

[0127] Although the control unit 50 detects the minimum point of the current fluctuation as information indicating the amount of current fluctuation and uses this information to control the motor 20, this is not a limitation. For example, the control unit 50 may detect when the amount of current fluctuation exceeds a threshold and use this information to control the motor. Even in this embodiment, it is possible to reduce the effects of variations in the absolute value of the voltage due to battery consumption, etc. Alternatively, other inflection points of the current fluctuation may be detected and used to control the motor. Furthermore, an expected current fluctuation waveform may be prepared in advance, and the motor may be controlled based on a comparison with the actual current fluctuation waveform. However, since the minimum point of the current fluctuation is a characteristic that occurs when the plunger transitions from top dead center to bottom dead center, detecting the minimum point facilitates stable position control of the plunger.

[0128] A known current detection circuit can be used as a means for acquiring current information that forms the basis of current fluctuation information. Specifically, current information can be acquired by passing a portion of the winding current through a resistive element to generate a minute voltage corresponding to the winding current, amplifying the voltage using a voltage amplifier circuit, and supplying the amplified voltage to the CPU 50B. The CPU 50B may also include a current information acquisition unit and a current fluctuation information acquisition unit instead of or in addition to the voltage information acquisition unit and the voltage fluctuation information acquisition unit. The inflection point detection unit included in the CPU 50B can detect a minimum point when the current fluctuation information changes from negative to positive. These configurations can be realized by a processor (computer) included in the CPU 50B executing a computer program stored in a semiconductor memory capable of storing information in a non-volatile (sometimes called non-transient) manner.

[0129] [Fourth embodiment] A driving tool according to the fourth embodiment will be described below. Components having the same or similar functions as those in the other embodiments will be given the same names and will not be described again. The inventors of the present application have focused on the fact that the characteristics of a motor vary with temperature. A motor (especially a brushless motor) has a characteristic that, in a high-load range, the rotation speed decreases at high temperatures compared to normal temperatures. On the other hand, in a low-load range, the rotation speed increases at high temperatures compared to normal temperatures.

[0130] On the other hand, in the driving tools and the like according to each embodiment, the motor is under high load near the top dead center and under low load when the deceleration control starts thereafter. Therefore, at high temperatures, the rotation speed of the motor near the top dead center is lower than the rotation speed at room temperature, while the rotation speed of the motor during the deceleration control period is higher than the rotation speed at room temperature. Therefore, if the same deceleration control is applied at high temperatures as at room temperature (low temperature), the stopping position of the plunger may be shifted toward the top dead center.

[0131] Therefore, the driving tool according to this embodiment further includes a temperature sensor that acquires temperature information indicating the motor temperature in addition to the driving tools according to the other embodiments, and a control unit that controls the motor based on this temperature information. More specifically, the low-temperature stop control applied at room temperature (low temperature) and the high-temperature stop control applied at high temperature are different. If the high-temperature stop control is applied at room temperature, the plunger will stop at a position closer to the bottom dead center than its intended stop position. If the low-temperature stop control is applied at high temperature, the plunger will stop at a position closer to the top dead center than its intended stop position. For example, the stop determination time is corrected based on temperature information, and the stop determination time is set shorter at high temperatures than at room temperature (low temperature). Note that the stop determination may be based on the motor rotation amount rather than time. In this case, the control unit is configured to execute the stop determination when the actual motor rotation amount reaches a predetermined motor rotation amount. The predetermined motor rotation amount is corrected according to temperature.

[0132] By adopting such a configuration, it is possible to stabilize the stopping position of the plunger. The above configuration may be applied to the driving tool 10 according to the first embodiment, or to other driving tools. Furthermore, the temperature detection may be configured to detect the motor temperature, or may be information correlated with the motor temperature (e.g., the temperature near the inverter circuit, the temperature of the switching element, the temperature on the circuit board, etc.). For example, instead of acquiring temperature information indicating the motor temperature, the driving tool according to this embodiment may be modified to acquire the temperature of an electrical component other than the motor (e.g., the switching element of the inverter circuit), and the motor may be controlled based on the acquired temperature information.

[0133] Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention. For example, some components of one embodiment can be added to other embodiments within the scope of ordinary creativity of a person skilled in the art. Also, some components of one embodiment can be replaced with corresponding components of other embodiments.

[0134] For example, some of the components that can be mounted on the driving tool according to the first embodiment may be applied to the driving tool according to the third embodiment. [Explanation of symbols]

[0135] 10 Driving tool 12 Housing 12A injection port 12B Grip 12C Bridge 12D nose 12E Trigger 12F Trigger biasing member 14 Magazine 14A Pusher 20 Motor 22 gears 22A 1st gear 22B 2nd gear 24 PCB boards 30 Plunger Assembly 32 Plunger 32A 1st side wall part 32A1 Gear engagement part 32A2 Wire engagement part 32B 2nd side wall part 32C 3rd side wall part 32C1 Driver engagement part 32D 4th side wall part 34 Drivers 36 Coil spring 36A One end of coil spring 36B Other end of coil spring 38 Moving parts 38A pin 38B Annular part 40 wire 42 Pulley 44 cylinders 44A Cylindrical part 44B hole 44C Cap 46 Guide rail B Battery DR1 Launch direction DR2 Departure direction F fastener

Claims

1. A plunger; a motor for moving the plunger from the bottom dead center to the top dead center; a driving means for driving the plunger from a top dead center to a bottom dead center, thereby driving the fastener using the plunger; a voltage fluctuation information acquiring means for acquiring voltage fluctuation information indicating a fluctuation amount of a voltage applied to the motor while the plunger is moving; a control means for controlling the motor based on the voltage fluctuation information; Equipped with The driving tool is characterized in that the control means determines the timing to start braking to stop the motor based on the rotational speed of the motor when an inflection point is detected in the amount of fluctuation in the voltage.

2. A plunger; a motor for moving the plunger from the bottom dead center to the top dead center; a driving means for driving the plunger from a top dead center to a bottom dead center, thereby driving the fastener using the plunger; a current fluctuation information acquiring means for acquiring current fluctuation information indicating a fluctuation amount of a current flowing through the motor while the plunger is moving; a control means for controlling the motor based on the current fluctuation information; Equipped with The driving tool is characterized in that the control means determines a braking start timing for stopping the motor based on the rotational speed of the motor when an inflection point is detected in the amount of fluctuation in the current.

3. A plunger; a motor for moving the plunger from the bottom dead center to the top dead center; a driving means for driving the plunger from a top dead center to a bottom dead center, thereby driving the fastener using the plunger; a speed information acquiring means for acquiring speed information indicating a moving speed of the plunger after the plunger has moved from the top dead center to the bottom dead center; control means for controlling the motor based on the speed information; Equipped with The driving tool is characterized in that the control means controls the motor so that the braking start timing for stopping the motor is earlier when the moving speed of the plunger is relatively high compared to when the moving speed of the plunger is relatively low.

4. A plunger; a motor for moving the plunger from the bottom dead center to the top dead center; a driving means for driving the fastener using the plunger by moving the plunger from the top dead center to the bottom dead center; A driving tool comprising: temperature information acquiring means for acquiring temperature information of electrical components mounted on the driving tool; a control means for controlling the motor based on the temperature information; Equipped with The driving tool is characterized in that the control means controls the motor so that the braking start timing for stopping the motor is earlier when the temperature of the electrical components is relatively high compared to when the temperature of the electrical components is relatively low.

5. a battery for applying a voltage to the motor; the voltage fluctuation information acquisition means is configured to acquire information indicating a fluctuation amount of a power supply voltage of the battery as the voltage fluctuation information. The driving tool according to claim 1 .

Images