JP7262058B2 - Electric tool - Google Patents

Description

FIELD OF THE DISCLOSURE The present disclosure relates generally to power tools, and more particularly to power tools that work with screws.

An impact tool (power tool) described in Patent Document 1 has a motor, a drive shaft, an output shaft, and a socket (tip tool). Rotation of the motor is transmitted to the output shaft via the drive shaft. The output shaft is connected to the socket. The socket has a square hole into which the head of a bolt (screw) or nut, which is a member to be tightened, is fitted.

JP 2015-193062 A

In an electric power tool such as the impact tool described in Patent Document 1, cam-out may occur, which is a phenomenon in which a tip tool such as a socket comes off a screw such as a bolt during operation of the electric power tool.

An object of the present disclosure is to provide an electric power tool capable of reducing the possibility of cam-out.

A power tool according to an aspect of the present disclosure includes an electric motor, a torque transmission section, a cam-out sensor, a control section, and an impact mechanism . The torque transmission section transmits the torque of the electric motor to the tool bit. The come-out sensor detects a change in physical quantity associated with a sign of come-out. The cam-out is a phenomenon in which the end tool and the screw are disengaged during operation of the electric motor. The screw is a member to be worked by the tip tool. The control section controls at least one of the electric motor and the torque transmission section based on the detection result of the cam-out sensor. The impact mechanism performs an impact operation to generate an impact force acting on the tool bit based on the power of the electric motor. The cam-out sensor has a measuring portion that measures a pressing force, which is a force with which the tip tool is pressed against the screw. The control unit determines whether there is a sign of cam-out based on the pressing force measured by the measuring unit, and controls at least one of the electric motor and the torque transmission unit based on the determination result. The control unit determines that there is a sign of the cam-out when the pressing force measured by the measurement unit is equal to or less than a threshold. The threshold takes a different value depending on whether the impact mechanism is performing the hitting action or not.

The present disclosure has the advantage of reducing the likelihood of cam-out occurring.

FIG. 1 is a perspective view of a power tool according to one embodiment. FIG. 2 is a cross-sectional view of the same power tool. FIG. 3 is a perspective view of a main part of the power tool same as the above. FIG. 4 is a cross-sectional view of a screw to be worked by the power tool. FIG. 5 is an enlarged cross-sectional view of a main part of the power tool according to Modification 1. FIG. FIG. 6 is an enlarged cross-sectional view of a main part of a power tool according to Modification 2. As shown in FIG.

(1) Outline A power tool 1 according to an embodiment will be described below with reference to the drawings. However, the embodiment described below is but one of the various embodiments of the present disclosure. The embodiments described below can be modified in various ways according to design and the like as long as the objects of the present disclosure can be achieved. Each drawing described in the following embodiments is a schematic drawing, and the ratio of the size and thickness of each component in the drawing does not necessarily reflect the actual dimensional ratio. .

The power tool 1 of this embodiment includes an electric motor 3, a torque transmission section 4, a cam-out sensor 8, and a control section 7, as shown in FIGS. The torque transmission section 4 transmits the torque of the electric motor 3 to the tip tool 62 . The come-out sensor 8 detects a change in physical quantity associated with a sign of come-out. Cam-out is a phenomenon in which the fitting between the tip tool 62 and the screw 9 is released while the electric motor 3 is in operation. The screw 9 is a member to be worked by the tip tool 62 . The control unit 7 controls at least one of the electric motor 3 and the torque transmission unit 4 based on the detection result of the cam-out sensor 8 .

According to this embodiment, the possibility of cam-out occurring can be reduced. That is, before the cam-out occurs, the cam-out sensor 8 can detect in advance the change in the physical quantity associated with the sign of the cam-out. By controlling the electric motor 3 based on the detection result of the cam-out sensor 8, the control unit 7 can prevent cam-out. Moreover, even if a cam-out occurs, measures such as stopping the electric motor 3 can be taken early.

(2) Configuration The configuration of the power tool 1 will be described in more detail. In the following description, the direction in which the drive shaft 41 and the output shaft 61 are aligned is defined as the front-rear direction. side to back. Further, in the following description, the direction in which the body portion 21 and the grip portion 22 are arranged is defined as the vertical direction, and the side of the body portion 21 as viewed from the grip portion 22 is defined as the upper side. Let the part 22 side be the bottom.

The power tool 1 of this embodiment is a portable power tool. The power tool 1 includes an electric motor 3 , a torque transmission section 4 , a cam-out sensor 8 , a control section 7 , an output shaft 61 , a first housing 2 and a trigger volume 23 .

The first housing 2 accommodates the electric motor 3 , the torque transmission section 4 , the cam-out sensor 8 , the control section 7 , and part of the output shaft 61 . The first housing 2 has a body portion 21 and a grip portion 22 . The body portion 21 has a cylindrical shape. The grip portion 22 protrudes from the body portion 21 .

The trigger volume 23 protrudes from the grip portion 22 . The trigger volume 23 is an operation unit that receives an operation for controlling rotation of the electric motor 3 . In addition, in the present disclosure, “rotation of the electric motor 3 ” means rotation of the rotation shaft 311 of the electric motor 3 . By pulling the trigger volume 23, the electric motor 3 can be turned on and off. In addition, the rotation speed of the electric motor 3 can be adjusted by the amount of pull when the trigger volume 23 is pulled. The rotation speed of the electric motor 3 increases as the retraction amount increases. The control unit 7 rotates or stops the electric motor 3 and controls the rotational speed of the electric motor 3 according to the amount of pull of the operation of pulling the trigger volume 23 . In the power tool 1 of this embodiment, the tip tool 62 (bit) is attached to the output shaft 61 . The output shaft 61 receives the rotational force of the electric motor 3 and rotates together with the tip tool 62 . By controlling the rotation speed of the electric motor 3 by operating the trigger volume 23, the rotation speed of the tip tool 62 is controlled.

The tip tool 62 is, for example, a driver bit. The tip tool 62 of this embodiment is a Phillips screwdriver bit with a tip portion 620 formed in a + (plus) shape. The tip tool 62 is fitted with a screw 9 (bolt, screw, or the like) to be worked. By rotating the tip tool 62 in a state where the tip tool 62 is fitted with the screw 9, the screw 9 can be tightened or loosened. The screw 9 includes a head 91 and a threaded portion 92 . The shape of the head 91 is disc-shaped. The threaded portion 92 protrudes from the head portion 91 . The head 91 has a plus-shaped screw hole 910 (see FIG. 4). In this embodiment, the state in which the tip 620 of the tip tool 62 is at least partially inserted into the threaded hole 910 of the screw 9 is referred to as the tip tool 62 and the screw 9 being fitted. Further, it means that the tip portion 620 of the tip tool 62 comes out of the screw hole 910 from the state in which the tip tool 62 and the screw 9 are engaged during the operation (rotation) of the electric motor 3. It is said that a phenomenon in which the fitting between 62 and screw 9 is released, that is, a cam-out occurs. When the tip portion 620 is in the screw hole 910 and it is predicted that cam-out will occur, it is said that there is a sign of cam-out. For example, as will be described later, if the pressing force from the tip tool 62 to the screw 9 increases at a predetermined rate of change or more, it is predicted that the tip 620 will be pushed back by the reaction force from the screw 9 and come out. , the control unit 7 determines that there is a sign of coming out.

A rechargeable battery pack is detachably attached to the power tool 1 . The power tool 1 operates using a battery pack as a power source. That is, the battery pack is a power source that supplies current to drive the electric motor 3 . A battery pack is not a component of the power tool 1 . However, the power tool 1 may have a battery pack. A battery pack includes an assembled battery configured by connecting a plurality of secondary batteries (for example, lithium ion batteries) in series, and a case accommodating the assembled battery.

The electric motor 3 is, for example, a brushless motor. In particular, the electric motor 3 of this embodiment is a synchronous motor, more specifically, a permanent magnet synchronous motor (PMSM). The electric motor 3 includes a rotor 31 having a rotating shaft 311 and permanent magnets 312 and a stator 32 having coils 321 . Electromagnetic interaction between the permanent magnets 312 and the coils 321 causes the rotor 31 to rotate with respect to the stator 32 .

Also, the electric motor 3 is a servo motor. The torque and rotation speed of the electric motor 3 change according to control by the controller 7 (servo driver). More specifically, the control unit 7 controls the operation of the electric motor 3 by feedback control that controls the torque and rotation speed of the electric motor 3 to approach target values. Further, the control unit 7 changes the control over the electric motor 3 by changing the torque target value and the rotation speed target value (speed target value) according to the detection result of the cam-out sensor 8 . As an example, the control unit 7 performs vector control. Vector control is a type of motor control method that separates the current supplied to the electric motor 3 into a current component that generates torque (rotational force) and a current component that generates magnetic flux, and controls each current component independently. be.

Further, the control unit 7 controls the rotation speed of the electric motor 3 so that the rotation speed of the electric motor 3 is within a predetermined range, and also controls the rotation speed of the electric motor 3 based on the detection result of the cam-out sensor 8 . More specifically, when the rotation speed target value determined based on the detection result of the cam-out sensor 8 is larger than the predetermined range, the control unit 7 changes the rotation speed target value to the upper limit value of the predetermined range. Further, when the rotation speed target value determined based on the detection result of the cam-out sensor 8 is smaller than the predetermined range, the control unit 7 changes the rotation speed target value to the lower limit value of the predetermined range.

The output shaft 61 holds the tip tool 62 . More specifically, the tip tool 62 can be attached to and detached from the output shaft 61 . The output shaft 61 transmits the torque of the electric motor 3 from the torque transmission portion 4 to the tip tool 62 . This causes the tip tool 62 to rotate.

The torque transmission section 4 has an impact mechanism 40 . The power tool 1 of the present embodiment is an electric impact driver that tightens a screw while performing an impact operation by an impact mechanism 40 . The impact mechanism 40 generates an impact force based on the power of the electric motor 3 in the impact operation, and the impact force acts on the tip tool 62 .

The torque transmission section 4 has a planetary gear mechanism 48 in addition to the impact mechanism 40 . Impact mechanism 40 includes drive shaft 41 , hammer 42 , return spring 43 , anvil 45 and two steel balls 49 . Rotation of the rotating shaft 311 of the electric motor 3 is transmitted to the drive shaft 41 via the planetary gear mechanism 48 . The torque transmission section 4 transmits the torque of the electric motor 3 to the tool bit 62 via the drive shaft 41 . The drive shaft 41 is arranged between the electric motor 3 and the output shaft 61 .

The control unit 7 changes the rotational speed of the electric motor 3 and the gear ratio of the planetary gear mechanism 48 based on the detection result of the cam-out sensor 8 . As a result, the rotation speed of the drive shaft 41 changes.

The hammer 42 moves relative to the anvil 45 and receives power from the electric motor 3 to apply a rotational impact to the anvil 45 . As shown in FIGS. 2 and 3, the hammer 42 includes a hammer body 420 and two projections 425. As shown in FIGS. The two protrusions 425 protrude from the surface of the hammer body 420 on the output shaft 61 side. The hammer body 420 has a through hole 421 through which the drive shaft 41 is passed. Further, the hammer body 420 has two grooves 423 on the inner peripheral surface of the through hole 421 . The drive shaft 41 has two grooves 413 on its outer peripheral surface. The two grooves 413 are connected. Two steel balls 49 are sandwiched between the two grooves 423 and the two grooves 413 . The two grooves 423, the two grooves 413 and the two steel balls 49 form a cam mechanism. The hammer 42 is movable relative to the drive shaft 41 in the axial direction of the drive shaft 41 and rotatable relative to the drive shaft 41 while the two steel balls 49 are moving. As the hammer 42 moves toward or away from the output shaft 61 along the axial direction of the drive shaft 41 , the hammer 42 rotates with respect to the drive shaft 41 .

The anvil 45 is formed integrally with the output shaft 61 . Anvil 45 holds tip tool 62 via output shaft 61 . Anvil 45 includes an anvil body 450 and two claws 455 . The anvil body 450 has an annular shape. The two claw portions 455 protrude from the anvil body 450 in the radial direction of the anvil body 450 . The anvil 45 faces the hammer body 420 in the axial direction of the drive shaft 41 . Further, when the impact mechanism 40 is not performing an impact operation, the two projections 425 of the hammer 42 and the two claws 455 of the anvil 45 are in contact with each other in the rotation direction of the drive shaft 41, and the hammer 42 and the anvil 45 are in contact with each other. rotate together. Therefore, at this time, the drive shaft 41, the hammer 42, the anvil 45, and the output shaft 61 rotate together.

A return spring 43 is sandwiched between the hammer 42 and the planetary gear mechanism 48 . The return spring 43 of this embodiment is a conical coil spring. The impact mechanism 40 further includes a plurality of (two in FIG. 2) steel balls 50 sandwiched between the hammer 42 and the return spring 43 and a ring 51 . Thereby, the hammer 42 is rotatable with respect to the return spring 43 . The hammer 42 receives a force directed toward the output shaft 61 from the return spring 43 in the axial direction of the drive shaft 41 .

Hereinafter, the movement of the hammer 42 toward the output shaft 61 in the axial direction of the drive shaft 41 is referred to as "the forward movement of the hammer 42". Further, hereinafter, the movement of the hammer 42 away from the output shaft 61 in the axial direction of the drive shaft 41 is referred to as "retraction of the hammer 42".

The impact mechanism 40 starts an impact operation when the load torque reaches or exceeds a predetermined value. That is, as the load torque increases, the component of the force generated between the hammer 42 and the anvil 45 that causes the hammer 42 to move backward also increases. When the load torque reaches or exceeds a predetermined value, the hammer 42 retreats while compressing the return spring 43 . As the hammer 42 retreats, the hammer 42 rotates while the two projections 425 of the hammer 42 climb over the two claws 455 of the anvil 45 . After that, the hammer 42 moves forward by receiving the restoring force from the returning spring 43 . Then, when the drive shaft 41 rotates approximately halfway, the two projections 425 of the hammer 42 collide with the side surfaces 4550 of the two claws 455 of the anvil 45 . In the impact mechanism 40, the two projections 425 of the hammer 42 collide with the two claws 455 of the anvil 45 each time the drive shaft 41 rotates approximately halfway. In other words, the hammer 42 applies a rotational impact to the anvil 45 each time the drive shaft 41 makes approximately half a turn.

Thus, in the impact mechanism 40, collisions between the hammer 42 and the anvil 45 occur repeatedly. The torque generated by this collision allows the screw 9 to be tightened more strongly than when there is no collision.

A first example of a mechanism that causes cam-out in the power tool 1 will be described below. When the rotation speed of the electric motor 3 is unstable, the hammer 42 advances to the front end of its movable range, and as a result, the pressing force from the tip tool 62 to the screw 9 may momentarily increase. After that, a reaction from the screw 9 to the tip tool 62 may separate the tip tool 62 from the screw 9 and cam-out may occur.

Next, a second example of the mechanism by which cam-out occurs in the power tool 1 will be described. A taper surface 911 is provided in the screw hole 910 (see FIG. 4) of the screw 9, and when a force in a direction crossing the axial direction of the screw 9 is applied from the tip tool 62 to the taper surface 911, the tip tool 62 It may move out of the threaded hole 910 along the tapered surface 911 . That is, come-out may occur. For example, when the component of the force applied to the screw 9 from the tip tool 62 in the direction intersecting the axial direction of the screw 9 is relatively large because the tip tool 62 is oriented obliquely with respect to the screw 9, the second A camout can occur with the example mechanism. Moreover, when the pressing force from the tip tool 62 to the screw 9 is insufficient with respect to the number of rotations of the electric motor 3, cam-out may occur with the mechanism of the second example.

A cam-out may occur due to the mechanism described in the first example, the mechanism described in the second example, or both.

The power tool 1 further includes a holding base 11 , a second housing 12 , a drive circuit 13 , a fan 14 , a cover 15 , bearings 16 and 17 . These are housed in the first housing 2 .

The shape of the holding table 11 is a cylindrical shape with a bottom. The holding base 11 holds a planetary gear mechanism 48 inside thereof. That is, the holding base 11 rotatably holds the gears of the planetary gear mechanism 48 . Further, the holding base 11 holds bearings 17 . The bearing 17 held by the holding base 11 and the bearing 16 held by the cover 15 rotatably hold the rotating shaft 311 of the electric motor 3 . That is, the holding base 11 rotatably holds the rotating shaft 311 via the bearing 17 . A rotating shaft 311 of the electric motor 3 is inserted into a through hole formed in the bottom surface of the holding base 11 and connected to the planetary gear mechanism 48 .

The shape of the second housing 12 is cylindrical. The diameter of the second housing 12 is smaller toward the front. The second housing 12 accommodates the holding base 11 and the torque transmission section 4 .

The holding base 11 is in contact with the second housing 12 . More specifically, both the cross-sectional shape of the front portion of the holding table 11 and the cross-sectional shape of the second housing 12 are annular, and the holding table 11 is inscribed in the second housing 12 . The holding base 11 is surrounded by a second housing 12 . The second housing 12 is surrounded by the first housing 2 .

The holding table 11 is in contact with the first housing 2 . More specifically, the rear portion of the holding base 11 and the inner surface of the first housing are in contact with each other.

The drive circuit 13 is arranged behind the electric motor 3 . Drive circuit 13 includes a substrate 130, a plurality of power elements, and a rotary sensor. Each power element is, for example, a FET (Field Effect Transistor) element. A rotary sensor includes, for example, a Hall IC. A rotary sensor detects the rotation angle of the rotor 31 of the electric motor 3 .

The control unit 7 controls the electric motor 3 via the drive circuit 13 . That is, the control unit 7 controls power supplied to the electric motor 3 via the plurality of FET elements by switching on and off the plurality of FET elements of the drive circuit 13 .

Also, the control unit 7 switches the gear ratio of the planetary gear mechanism 48 . That is, the controller 7 switches gears of the planetary gear mechanism 48 . The control unit 7 switches gears by, for example, driving an actuator to slide the gears of the planetary gear mechanism 48 .

The fan 14 is arranged between the electric motor 3 and the holding base 11 . The fan 14 generates wind that flows forward. Thereby, the fan 14 air-cools the internal space of the first housing 2 .

The cover 15 is arranged behind the drive circuit 13 . A cover 15 covers the drive circuit 13 . The inner surface shape of the rear end portion of the first housing 2 and the outer surface shape of the cover 15 substantially match. The inner surface of the first housing 2 and the outer surface of the cover 15 are in contact with each other.

The cam-out sensor 8 has a measuring section 80 . The cam-out sensor 8 of this embodiment consists of only the measuring section 80 . The measurement unit 80 measures pressing force. The pressing force is the force with which the tip tool 62 is pressed against the screw 9 . That is, the pressing force is a force acting on the screw 9 in the axial direction (forward direction) of the tip tool 62 . The control unit 7 controls at least one of the electric motor 3 and the torque transmission unit 4 based on the pressing force measured by the measurement unit 80 . As a result, it is possible to reduce the possibility of cam-out occurring. More specifically, the control unit 7 reduces the torque transmitted from the electric motor 3 to the output shaft 61 via the torque transmission unit 4 as the pressing force measured by the measurement unit 80 decreases. Further, for example, when the pressing force measured by the measuring unit 80 is equal to or greater than a predetermined value, the control unit 7 sets the gear ratio of the planetary gear mechanism 48 to the first gear ratio, and when the pressing force is less than the predetermined value, The gear ratio of the planetary gear mechanism 48 is set to a second gear ratio that is smaller than the first gear ratio.

The pressing force varies depending on the magnitude of the force applied by the operator of the electric power tool 1 while gripping it, vibrations generated by the striking operation of the impact mechanism 40, and the like. The pressing force is a physical quantity that changes with a sign of cam-out.

The measurement unit 80 is, for example, a strain sensor (strain gauge). The measurement unit 80 of this embodiment is a resistive strain sensor. The strain sensor of this embodiment is attached to the surface of the output shaft 61 . A strain sensor (measuring unit 80 ) measures the strain of the output shaft 61 . The strain of the output shaft 61 is a physical quantity that correlates with the pressing force from the tip tool 62 to the screw 9 . The strain sensor converts an electrical resistance value corresponding to the strain generated by applying torque to the output shaft 61 into a voltage signal and outputs it as a detection result.

The controller 7 includes a computer system with one or more processors and memory. At least part of the functions of the control unit 7 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in a memory, provided through an electric communication line such as the Internet, or recorded in a non-temporary recording medium such as a memory card and provided.

The control unit 7 determines whether or not there is a sign of cam-out based on the pressing force measured by the measuring unit 80, and controls at least one of the electric motor 3 and the torque transmission unit 4 based on the determination result. The control unit 7 determines that there is a sign of cam-out when the amount of change per unit time of the pressing force measured by the measuring unit 80 is equal to or greater than a predetermined value (first threshold value).

That is, as explained in the first example of the mechanism that causes cam-out, the pressing force from the tip tool 62 to the screw 9 momentarily increases, and then the reaction from the screw 9 to the tip tool 62 causes the tip tool 62 to become unthreaded. Away from 9, come-out can occur. The momentary increase in the pressing force from the tip tool 62 to the screw 9 also increases the amount of change in the pressing force per unit time. Therefore, the control unit 7 can determine whether or not there is a sign of cam-out by monitoring the amount of change in the pressing force per unit time.

Further, when the pressing force measured by the measuring unit 80 is equal to or less than the second threshold value, the control unit 7 determines that there is a sign of cam-out.

That is, as described in the second example of the mechanism that causes cam-out, cam-out may occur when the pressing force from the tip tool 62 to the screw 9 is insufficient for the rotational speed of the electric motor 3. Therefore, the control unit 7 can determine whether there is a sign of cam-out by monitoring the magnitude of the pressing force.

The first threshold and the second threshold are recorded in advance in the memory of the controller 7, for example.

It should be noted that the first threshold value may take different values depending on whether the impact mechanism 40 is performing an impact operation or not. Similarly, the second threshold value may take different values depending on whether the impact mechanism 40 is performing an impact operation or not.

When the controller 7 determines that there is a sign of cam-out based on the detection result of the cam-out sensor 8 , it reduces the rotation speed of the electric motor 3 . As a result, the number of revolutions of the drive shaft 41 is reduced, so that the magnitude of the striking force in the striking operation of the impact mechanism 40 is reduced. As a result, the force applied from the tip tool 62 to the screw 9 is reduced. Further, the force (reaction force) acting on the tip tool 62 from the screw 9 in the direction of separating the tip tool 62 from the screw 9 is reduced. As a result, the possibility of cam-out occurring can be reduced. In the present disclosure, reducing the rotation speed of the electric motor 3 also includes setting the rotation speed of the electric motor 3 to 0 (stopping).

In addition, since the rotation speed of the drive shaft 41 is reduced, the interval between impact forces generated in the impact operation of the impact mechanism 40 (that is, the cycle of collision between the hammer 42 and the anvil 45) is lengthened, which may cause cam-out. can be reduced.

When the control unit 7 does not determine that there is a sign of cam-out, the greater the pressing force measured by the cam-out sensor 8 (measurement unit 80), the more the rotation speed of the electric motor 3 is increased. As a result, the screw 9 can be tightened (or loosened) in a state in which the larger the pressing force, the larger the torque.

(Modification 1)
The power tool 1 according to Modification 1 will be described below with reference to FIG. Configurations similar to those of the embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The measurement unit 80 of Modification 1 measures the pressure generated between the holding base 11 and the first housing 2 (housing). In this respect, Modification 1 differs from the embodiment. The pressure generated between the holding base 11 and the first housing 2 is a physical quantity that correlates with the pressing force from the tip tool 62 to the screw 9 . Further, the holding base 11 holds the planetary gear mechanism 48 of the torque transmission section 4 inside thereof. The first housing 2 surrounds the holding base 11 . A more detailed description will be given below.

The measurement unit 80 is a pressure sensor. The measurement unit 80 is, for example, a strain sensor. The strain sensor is formed in a sheet shape. As shown in FIG. 5, the measuring section 80 is sandwiched between the holding base 11 and the first housing 2 . A portion of the holding base 11 sandwiching the measuring portion 80, the measuring portion 80, and a portion of the body portion 21 of the first housing 2 sandwiching the measuring portion 80 are arranged in the front-rear direction.

As the rotation shaft 311 of the electric motor 3 rotates, the gears of the planetary gear mechanism 48 rotate. The holding table 11 holding the rotating shaft 311 and the planetary gear mechanism 48 is subjected to pressure due to the rotating torque of the rotating shaft 311 and the rotating torque of the gears of the planetary gear mechanism 48 . Therefore, pressure is generated between the holding table 11 and the first housing 2 and this pressure is measured by the measuring section 80 . The pressure measured by the measuring unit 80 is the pressure due to the force along the axial direction (front-rear direction) of the drive shaft 41 . The control unit 7 controls at least one of the electric motor 3 and the torque transmission unit 4 based on the pressing force measured by the measurement unit 80 .

Note that the second housing 12 instead of the first housing 2 may function similarly to the first housing 2 of the first modification. That is, the measurement unit 80 may measure the pressure generated between the holding table 11 and the second housing 12 surrounding the holding table 11 .

(Modification 2)
The power tool 1 according to Modification 2 will be described below with reference to FIG. 6 . Configurations similar to those of the embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The measurement unit 80 of Modification 2 measures the pressure generated between the electric motor 3 and the first housing 2 (housing) surrounding the electric motor 3 . In this respect, Modification 2 differs from the embodiment. The pressure generated between the electric motor 3 and the first housing 2 is a physical quantity that correlates with the pressing force from the tip tool 62 to the screw 9 . A more detailed description will be given below.

The measurement unit 80 is a pressure sensor. The measurement unit 80 is, for example, a strain sensor. As shown in FIG. 6, the measuring section 80 is sandwiched between the cover 15 and the bearing 16. As shown in FIG. A portion of the cover 15 sandwiching the measuring section 80, the measuring section 80, and the bearing 16 are arranged in the front-rear direction.

As the rotating shaft 311 of the electric motor 3 rotates, pressure is applied to the bearing 16 by the rotational torque of the rotating shaft 311 . Therefore, a pressure is generated between the bearing 16 and the cover 15, and this pressure is measured by the measuring section 80. FIG. The pressure measured by measuring unit 80 correlates with the pressure generated between electric motor 3 and first housing 2 . The pressure measured by the measuring unit 80 is the pressure due to the force along the axial direction (front-rear direction) of the rotating shaft 311 of the electric motor 3 . The control unit 7 controls at least one of the electric motor 3 and the torque transmission unit 4 based on the pressing force measured by the measurement unit 80 .

Note that the measuring section 80 may be sandwiched between the first housing 2 and the bearing 16 . That is, the measuring section 80 may measure the pressure generated between the first housing 2 and the bearing 16 .

(Other modifications of the embodiment)
Other modifications of the embodiment are listed below. The following modified examples may be implemented in combination as appropriate. Moreover, the following modifications may be realized by appropriately combining with each of the modifications described above.

A strain sensor as the measurement unit 80 may be attached to the drive shaft 41 instead of the output shaft 61 to measure the strain of the drive shaft 41 . Alternatively, the strain sensor may be sandwiched between the bearing 17 and the pedestal 11 to measure the pressure developed between the electric motor 3 and the pedestal 11 . In addition, the measurement unit 80 may be appropriately arranged at a position where strain or pressure correlated with the pressing force from the tip tool 62 to the screw 9 can be measured.

The measurement unit 80 is not limited to resistive strain sensors. The measurement unit 80 may be, for example, a magnetostrictive strain sensor capable of detecting torsional strain. A magnetostrictive strain sensor has a coil. The measurement unit 80 is arranged near the output shaft 61, for example. The measurement part 80 is fixed to the second housing 12 or the first housing 2, for example. The magnetostrictive strain sensor detects changes in magnetic permeability according to strain generated by applying torque to the output shaft 61 with the coils installed in the non-rotating portion near the output shaft 61, and generates a voltage proportional to the strain. A signal is output as the detection result.

The magnetostrictive strain sensor may be arranged near the electric motor 3 . The magnetostrictive strain sensor measures the strain of the rotating shaft 311 of the electric motor 3 . That is, the change in magnetic permeability corresponding to the strain generated by the torque applied to the rotating shaft 311 of the electric motor 3 is detected by a coil installed in the non-rotating portion near the electric motor 3, and the voltage signal proportional to the strain is Output as a detection result.

The first housing 2 and the second housing 12 may be formed as one member. The first housing 2 and the cover 15 may be formed as one member.

The control unit 7 may reduce the torque transmitted to the output shaft 61 when the pressing force measured by the measuring unit 80 is smaller than the first value. Also, the control unit 7 may increase the torque transmitted to the output shaft 61 when the pressing force measured by the measuring unit 80 is greater than the second value. The second value is greater than the first value. The first value may take different values depending on whether the impact mechanism 40 is performing an impact operation or not. Similarly, the second value may take different values depending on whether the impact mechanism 40 is performing an impacting operation or not.

The control unit 7 controls at least one of the electric motor 3 and the torque transmission unit 4 based on the detection result of the cam-out sensor 8 . Here, the control based on the detection result of the cam-out sensor 8 may be executed only when the impact mechanism 40 is performing the hitting operation. That is, the control section 7 may control the electric motor 3 and the torque transmission section 4 without using the detection result of the cam-out sensor 8 when the impact mechanism 40 is not performing the striking operation.

The control unit 7 of the embodiment controls the rotation speed of the electric motor 3 so that the rotation speed of the electric motor 3 is within a predetermined range (first range). On the other hand, the control unit 7 may control at least one of the electric motor 3 and the torque transmission unit 4 so that the rotation speed of the drive shaft 41 is within a predetermined range (second range). The second range is a range different from the first range.

A plurality of functions of the control unit 7 of the embodiment may be distributed in a plurality of configurations. For example, among the plurality of functions of the control unit 7, the function of controlling the electric motor 3 and the function of determining whether there is a sign of come-out may be provided separately.

The physical quantity detected by the cam-out sensor 8 is not limited to the pressing force from the tip tool 62 to the screw 9 . The come-out sensor 8 may detect a physical quantity whose value or rate of change differs between when there is a sign of come-out and when there is no sign of come-out.

In the embodiment, the tip tool 62 is not included in the configuration of the power tool 1 . However, the tip tool 62 may be included in the configuration of the power tool 1 .

Inside the first housing 2, the arrangement of the fan 14 and the arrangement of the drive circuit 13 may be reversed.

(summary)
The following aspects are disclosed from the embodiments and the like described above.

A power tool (1) according to a first aspect includes an electric motor (3), a torque transmission section (4), a cam-out sensor (8), and a control section (7). The torque transmission section (4) transmits the torque of the electric motor (3) to the tip tool (62). A come-out sensor (8) detects a change in physical quantity associated with a sign of come-out. Cam-out is a phenomenon in which the end tool (62) is disengaged from the screw (9) during operation of the electric motor (3). The screw (9) is a member to be worked by the tip tool (62). A control section (7) controls at least one of the electric motor (3) and the torque transmission section (4) based on the detection result of the cam-out sensor (8).

According to the above configuration, it is possible to reduce the possibility of cam-out occurring.

Moreover, in the power tool (1) according to the second aspect, in the first aspect, the cam-out sensor (8) has a measuring section (80). The measuring part (80) measures the pressing force, which is the force with which the tip tool (62) is pressed against the screw (9). A control section (7) controls at least one of the electric motor (3) and the torque transmission section (4) based on the pressing force measured by the measurement section (80).

According to the above configuration, the cam-out sensor (8) measures the pressing force, which is a physical quantity directly related to the occurrence of the cam-out, so that it is possible to improve the detection accuracy of the presence or absence of a sign of the cam-out.

Moreover, the electric power tool (1) according to the third aspect, in the second aspect, further includes an output shaft (61). The output shaft (61) holds a tip tool (62). The output shaft (61) transmits the torque of the electric motor (3) from the torque transmission section (4) to the tip tool (62). A measurement unit (80) measures the strain of the output shaft (61) as a physical quantity correlated with the pressing force.

According to the above configuration, the cam-out sensor (8) measures the distortion of the output shaft (61), which is a physical quantity that is relatively strongly correlated with the magnitude of the pressing force. can be made

In addition, the power tool (1) according to the fourth aspect, in the second aspect, further includes a holding base (11) and a housing (first housing (2)). The holding base (11) holds the torque transmission part (4). The housing encloses the holding platform (11). A measuring section (80) measures the pressure generated between the holding base (11) and the housing as a physical quantity correlated with the pressing force.

According to the above configuration, it is possible to easily secure an installation space for the cam-out sensor (8).

In the second aspect, the power tool (1) according to the fifth aspect further includes a housing (first housing (2)). A housing surrounds the electric motor (3). A measuring section (80) measures the pressure generated between the electric motor (3) and the housing as a physical quantity correlated with the pressing force.

According to the above configuration, it is possible to easily secure an installation space for the cam-out sensor (8).

Further, in the electric power tool (1) according to the sixth aspect, in any one of the second to fifth aspects, the control section (7) controls the cam-out based on the pressing force measured by the measuring section (80). Presence or absence of a sign of failure is determined, and at least one of the electric motor (3) and the torque transmission section (4) is controlled based on the determination result. A control unit (7) determines that there is a sign of cam-out when the amount of change per unit time of the pressing force measured by the measuring unit (80) is equal to or greater than a predetermined value.

According to the above configuration, the control section (7) can determine the presence or absence of a sign of come-out by simple processing.

Further, in the power tool (1) according to the seventh aspect, in any one of the first to sixth aspects, the control section (7) detects a sign of cam-out based on the detection result of the cam-out sensor (8). If it is determined that there is, the rotation speed of the electric motor (3) is reduced.

According to the above configuration, it is possible to reduce the possibility of cam-out occurring.

Further, in the power tool (1) according to the eighth aspect, in any one of the first to seventh aspects, the controller (7) controls the rotation speed of the electric motor (3) to be within a predetermined range. The rotation speed of the electric motor (3) is controlled, and the rotation speed of the electric motor (3) is controlled based on the detection result of the cam-out sensor (8).

According to the above configuration, it is possible to reduce the possibility that the operation of the electric power tool (1) becomes unstable due to the rotational speed of the electric motor (3) being out of the predetermined range.

Moreover, the power tool (1) according to the ninth aspect, in any one of the first to eighth aspects, further comprises an impact mechanism (40). The impact mechanism (40) performs a striking action. The impact operation is an operation for generating impact force acting on the tip tool (62) based on the power of the electric motor (3).

According to the above configuration, it is possible to reduce the possibility of cam-out occurring in the hitting motion.

Configurations other than the first aspect are not essential to the power tool (1) and can be omitted as appropriate.

1 electric tool 11 holding table 2 first housing (housing)
3 electric motor 4 torque transmission section 40 impact mechanism 61 output shaft 62 tip tool 7 control section 8 cam-out sensor 80 measurement section 9 screw

Claims (7)

an electric motor;
a torque transmission unit that transmits the torque of the electric motor to the tip tool;
a cam-out sensor that detects a change in physical quantity associated with a sign of cam-out, which is a phenomenon in which the end tool is disengaged from a screw to be worked by the end tool during operation of the electric motor;
a control unit that controls at least one of the electric motor and the torque transmission unit based on the detection result of the cam-out sensor;
an impact mechanism that performs an impact operation to generate an impact force acting on the tip tool based on the power of the electric motor ;
The cam-out sensor has a measuring unit that measures a pressing force that is the force with which the tip tool is pressed against the screw,
The control unit determines whether or not there is a sign of cam-out based on the pressing force measured by the measurement unit, and controls at least one of the electric motor and the torque transmission unit based on the determination result,
The control unit determines that there is a sign of the cam-out when the pressing force measured by the measurement unit is equal to or less than a threshold,
the threshold takes a different value depending on whether the impact mechanism is performing the hitting action or not;
Electric tool. an output shaft that holds the tip tool and transmits torque of the electric motor from the torque transmission portion to the tip tool;
The measurement unit measures the strain of the output shaft as a physical quantity that correlates with the pressing force.
The power tool according to claim 1. a holding base that holds the torque transmission part;
a housing surrounding the holding platform;
The measuring unit measures the pressure generated between the holding table and the housing as a physical quantity that correlates with the pressing force.
The power tool according to claim 1. further comprising a housing surrounding the electric motor;
The measuring unit measures the pressure generated between the electric motor and the housing as a physical quantity that correlates with the pressing force.
The power tool according to claim 1. The control unit determines that there is a sign of the cam-out when an amount of change per unit time of the pressing force measured by the measurement unit is equal to or greater than a predetermined value.
The power tool according to any one of claims 1-4. When the controller determines that there is a sign of the cam-out based on the detection result of the cam-out sensor, the controller reduces the rotation speed of the electric motor.
The power tool according to any one of claims 1-5. The control unit controls the rotation speed of the electric motor so that the rotation speed of the electric motor is within a predetermined range, and controls the rotation speed of the electric motor based on the detection result of the cam-out sensor.
The power tool according to any one of claims 1-6.

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