Patent ID: 12237738

DETAILED DESCRIPTION

Although one or more embodiments of the present disclosure will now be described with reference to the drawings, the present disclosure is not limited to the present embodiments. The components in the embodiments described below may be combined as appropriate. One or more components may be eliminated.

In the embodiments, the positional relationships between the components will be described using the directional terms such as right and left (or lateral), front and rear (or frontward and rearward), and up and down (or vertical). The terms indicate relative positions or directions with respect to the center of an electric work machine.

The electric work machine includes a motor. In the embodiments, a direction parallel to a rotation axis AX of the motor is referred to as an axial direction for convenience. A direction radial from the rotation axis AX of the motor is referred to as a radial direction or radially for convenience. A direction about the rotation axis AX of the motor is referred to as a circumferential direction, circumferentially, or a rotation direction for convenience. A direction parallel to a tangent of an imaginary circle about the rotation axis AX of the motor is referred to as a tangential direction for convenience.

A position nearer the rotation axis AX of the motor in the radial direction, or a radial direction toward the rotation axis AX, is referred to as radially inward for convenience. A position farther from the rotation axis AX of the motor in the radial direction, or a radial direction away from the rotation axis AX of the motor, is referred to as radially outside or radially outward for convenience. A position in one circumferential direction, or one circumferential direction, is referred to as a first circumferential direction for convenience. A position in the other circumferential direction, or the other circumferential direction, is referred to as a second circumferential direction for convenience. A position in one tangential direction, or one tangential direction, is referred to as a first tangential direction for convenience. A position in the other tangential direction, or the other tangential direction, is referred to as a second tangential direction for convenience.

First Embodiment

Electric Work Machine

FIG.1is a perspective view of an electric work machine1according to an embodiment as viewed from the front. The electric work machine1according to the present embodiment is an impact driver as an example of a power tool. As shown inFIG.1, the electric work machine1includes a housing2, a rear case3, a hammer case4, a battery mount5, a motor601, a fan7, an anvil8, a controller9, a trigger switch10, a forward-reverse switch lever11, an operation panel12, and a lamp13.

The housing2includes a motor compartment2A, a grip2B, and a controller compartment2C. The housing2is formed from a synthetic resin.

The motor compartment2A accommodates the motor601. The motor compartment2A is cylindrical.

The grip2B is grippable by an operator of the electric work machine1. The grip2B protrudes downward from a lower portion of the motor compartment2A.

The controller compartment2C accommodates the controller9. The controller compartment2C is connected to a lower end of the grip2B. The controller compartment2C has greater outer dimensions than the grip2B in the front-rear and lateral directions.

The rear case3is connected to the rear of the motor compartment2A to cover a rear opening of the motor compartment2A. The rear case3is formed from a synthetic resin.

The hammer case4is connected to the front of the motor compartment2A to cover a front opening of the motor compartment2A. The hammer case4is formed from a metal.

A battery pack14is attached to the battery mount5. The battery mount5is located below the controller compartment2C. The battery pack14is detachable from the battery mounts5. The battery pack14may be a secondary battery. The battery pack14in the present embodiment may be a rechargeable lithium-ion battery. The battery pack14is attached to the battery mount5to power the electric work machine1. The motor601is driven by power supplied from the battery pack14. The controller9operates with power supplied from the battery pack14.

The motor601is a power source for the electric work machine1. The motor601generates a rotational force for rotating the anvil8. The motor601is a brushless motor. In the present embodiment, the rotation axis AX of the motor601extends in the front-rear direction. The axial direction and the front-rear direction are parallel to each other.

The fan7generates an airflow for cooling the motor601. The fan7rotates with a rotational force generated by the motor601.

The motor compartment2A has inlets15. The rear case3has outlets16. The outlets16are located rearward from the inlets15. The inlets15connect the inside and the outside of the housing2. The outlets16connect the inside and the outside of the housing2. The inlets15are located in right and left portions of the motor compartment2A. The outlets16are located in right and left portions of the rear case3. As the fan7rotates, air outside the housing2flows into an internal space of the housing2through the inlets15to cool the motor601. Air inside the housing2flows out of the housing2through the outlets16.

The hammer case4accommodates a reducer, a spindle, and a striker. The reducer is located frontward from the motor601. The spindle is located at least partially frontward from the reducer. The reducer transmits a rotational force generated by the motor601to the spindle. The spindle rotates about the rotation axis AX with the rotational force transmitted from the motor601through the reducer. The reducer reduces the rotational speed of the spindle below the rotational speed of motor601. The striker strikes the anvil8in the rotation direction in response to rotation of the spindle.

The anvil8rotates about the rotation axis AX with a rotational force from the motor601. The anvil8has an insertion hole8A for receiving a tip tool. A chuck unit17for holding the tip tool at least partially surrounds the anvil8. The tip tool placed in the insertion hole8A is held by the chuck unit17.

The controller9controls the motor601. The controller9controls a drive current supplied from the battery pack14to the motor601. The controller9is accommodated in the controller compartment2C. The controller9includes a circuit board on which multiple electronic components are mounted. Examples of the electronic components mounted on the board include a processor such as a central processing unit (CPU), a nonvolatile memory such as a read-only memory (ROM) or a storage device, a volatile memory such as a random-access memory (RAM), a field-effect transistor (FET), and a resistor.

The trigger switch10drives the motor601. The trigger switch10is located on an upper portion of the grip2B. The trigger switch10protrudes frontward from an upper front portion of the grip2B. The trigger switch10is moved backward to drive the motor601. The trigger switch10stops being operated to stop the motor601.

The forward-reverse switch lever11is operable to change the rotation direction of the motor601. The forward-reverse switch lever11is located between the lower end of the motor compartment2A and the upper end of the grip2B. The forward-reverse switch lever11is moved leftward or rightward. The rotation direction of the motor601is switched to switch the rotation direction of the anvil8.

The operation panel12is located in the controller compartment2C. The operation panel12is a plate. The operation panel12includes multiple operation switches. The operation panel12outputs operation signals. The controller9changes the control mode of the motor601based on the operation signals output from the operation panel12. The control mode of the motor601refers to a method or a pattern for controlling the motor601.

The lamp13emits illumination light to illuminate ahead of the electric work machine1. The lamp13includes a light-emitting diode (LED). The lamp13is located at the upper front of the grip2B.

Motor

FIG.2is an exploded perspective view of the motor601in the present embodiment as viewed from the rear.FIG.3is an exploded perspective view of the motor601in the present embodiment as viewed from the front.FIG.4is an exploded perspective view of a stator20and a rotor301in the present embodiment as viewed from the rear.FIG.5is an exploded perspective view of the stator20and the rotor301in the present embodiment as viewed from the front.

The motor601in the present embodiment is a brushless inner-rotor motor. As shown inFIGS.2to5, the motor601includes the stator20and the rotor301rotatable relative to the stator20. The stator20surrounds the rotor301. The rotor301rotates about the rotation axis AX.

Stator

The stator20includes a stator core21, a front insulator22, a rear insulator23, coils24, power lines25, fusing terminals26, short-circuiting members27, and an insulating member28. The front insulator22and the rear insulator23may be integrally molded with and fixed to the stator core21.

The stator core21includes multiple steel plates stacked on one another. The steel plates are metal plates formed from iron as a main component. The stator core21is cylindrical. The stator core21includes multiple (six in the present embodiment) teeth21T to support the coils24. The teeth21T protrude radially inward from the inner surface of the stator core21.

The front insulator22is an electrical insulating member formed from a synthetic resin. The front insulator22is located on the front of the stator core21. The front insulator22is cylindrical. The front insulator22includes multiple (six in the present embodiment) protrusions22T to support the coils24. The protrusions22T protrude radially inward from the inner surface of the front insulator22.

The rear insulator23is an electrical insulating member formed from a synthetic resin. The rear insulator23is located on the rear of the stator core21. The rear insulator23is cylindrical. The rear insulator23includes multiple (six in the present embodiment) protrusions23T to support the coils24. The protrusions23T protrude radially inward from the inner surface of the rear insulator23.

Each tooth21T has a front end connecting to the rear end of the corresponding protrusion22T. Each tooth21T has a rear end connecting to the front end of the corresponding protrusion23T.

The coils24are attached to the stator core21with the front insulator22and the rear insulator23in between. The stator20includes multiple (six in the present embodiment) coils24. Each coil24is wound around the corresponding tooth21T with the protrusion22T and the protrusion23T in between. Each coil24surrounds the tooth21T, the protrusion22T, and the protrusion23T. The coils24and the stator core21are insulated from each other with the front insulator22and the rear insulator23in between.

The multiple coils24are formed by winding a single wire. The coils24adjacent in the circumferential direction are connected with a connection wire29, which is a part of the wire. The connection wire29is a part of the wire between two adjacent coils24. The connection wire29is supported on the front insulator22.

The power lines25are connected to the battery pack14with the controller9. The battery pack14serves as a power supply for the motor601. The battery pack14supplies a drive current to the motor601through the controller9. The controller9controls the drive current supplied from the battery pack14to the motor601. The drive current from the battery pack14is supplied to the power lines25through the controller9.

The fusing terminals26are connected to the coils24with the connection wire29. The fusing terminals26conduct electricity. Multiple (six in the present embodiment) fusing terminals26surround the rotation axis AX. The fusing terminals26are as many as the coils24.

The fusing terminals26are supported on the front insulator22. The front insulator22in the present embodiment includes supports22S for supporting the fusing terminals26. Six supports22S are located at intervals in the circumferential direction. Each support22S includes a pair of protrusions22P protruding frontward from the front surface of the front insulator22. Each fusing terminal26is held between the pair of protrusions22P and is thus supported by the support22S.

The connection wire29is supported by the support22S. The connection wire29is supported on the radially outer surface of the protrusion22P. Each fusing terminal26held between the pair of protrusions22P is connected to the connection wire29. The connection wire29is located inside a bent portion of the fusing terminal26. The fusing terminal26and the connection wire29are welded together. The fusing terminals26are thus connected to the connection wire29.

The short-circuiting members27connect the fusing terminals26and the power lines25. The short-circuiting members27conduct electricity. The short-circuiting members27are curved in a plane orthogonal to the rotation axis AX. The stator20includes multiple (three in the present embodiment) short-circuiting members27. Each short-circuiting member27short-circuits a single power line25and a pair of fusing terminals26. Each short-circuiting member27has an opening27A receiving a front portion of the fusing terminal26. Each fusing terminal26has the front portion received in the opening27A and is thus connected to the short-circuiting member27.

The insulating member28supports the power lines25and the short-circuiting members27. The insulating member28is formed from a synthetic resin. The insulating member28includes a body28A, screw bosses28B, and a support28C.

The body28A is annular. In the present embodiment, the short-circuiting members27are at least partially located in the body28A. The short-circuiting members27are fixed to the body28A by insert molding. The fusing terminals26are supported on the body28A with the short-circuiting members27in between. The body28A insulates three short-circuiting members27from one another.

The screw bosses28B protrude radially outward from the peripheral edge of the body28A. Four screw bosses28B are arranged on the peripheral edge of the body28A.

The support28C protrudes downward from a lower portion of the body28A. The support28C supports the power lines25.

The power lines25, the fusing terminals26, the short-circuiting members27, and the insulating member28are located frontward from the stator core21. The fusing terminals26are located at least partially rearward from the short-circuiting members27and the insulating member28.

FIG.6is a schematic diagram of the stator20in the present embodiment.FIG.7is a schematic diagram of the connected coils24in the present embodiment.

The six coils24are formed by winding a single wire in the present embodiment. As shown inFIGS.6and7, the wire includes a wind start portion29S first wound around one tooth21T. The wire is sequentially wound around each of the teeth21T adjacent in the circumferential direction to form the six coils24. The wire includes a wind end portion29E that is wound finally.

As shown inFIG.7, the battery pack14supplies a drive current to the power lines25through the controller9. The drive current supplied to the power lines25is fed to the fusing terminals26through the short-circuiting members27. The drive current fed to the fusing terminals26are fed to the coils24through the connection wire29.

In the present embodiment, the drive current includes a U-phase drive current, a V-phase drive current, and a W-phase drive current.

As shown inFIGS.4to7, the power lines25include a U-phase power line25U, a V-phase power line25V, and a W-phase power line25W. The U-phase power line25U receives a U-phase drive current. The V-phase power line25V receives a V-phase drive current. The W-phase power line25W receives a W-phase drive current.

The short-circuiting members27include a U-phase short-circuiting member27U, a V-phase short-circuiting member27V, and a W-phase short-circuiting member27W. The U-phase short-circuiting member27U is connected to the U-phase power line25U. The V-phase short-circuiting member27V is connected to the V-phase power line25V. The W-phase short-circuiting member27W is connected to the W-phase power line25W.

The fusing terminals26include a pair of U-phase fusing terminals26U, a pair of V-phase fusing terminals26V, and a pair of W-phase fusing terminals26W. The pair of U-phase fusing terminals26U are connected to the U-phase short-circuiting member27U. The pair of V-phase fusing terminals26V are connected to the V-phase short-circuiting member27V. The pair of W-phase fusing terminals26W are connected to the W-phase short-circuiting member27W.

Each of the six coils24is assigned to one of a U- (U-V-) phase, a V- (V-W-) phase, and a W- (W-U-) phase.

Each pair of coils24is assigned to the U-phase, the V-phase, or the W-phase. The six coils24include a pair of U-phase coils24U assigned to the U-phase, a pair of V-phase coils24V assigned to the V-phase, and a pair of W-phase coils24W assigned to the W-phase.

The pair of U-phase coils24U (U-phase coils24U1and24U2) face each other in the radial direction. The pair of V-phase coils24V (V-phase coils24V1and24V2) face each other in the radial direction. The pair of W-phase coils24W (W-phase coils24W1and24W2) face each other in the radial direction. As shown inFIG.6, the V-phase coil24V1is located adjacent to the U-phase coil24U1in the circumferential direction. The W-phase coil24W1is located adjacent to the V-phase coil24V1. The U-phase coil24U2is located adjacent to the W-phase coil24W1. The V-phase coil24V2is located adjacent to the U-phase coil24U2. The W-phase coil24W2is located adjacent to the V-phase coil24V2.

As shown inFIG.6, a first U-phase fusing terminal26U is connected to the connection wire29connecting the U-phase coil24U1and V-phase coil24V1adjacent in the circumferential direction. A second U-phase fusing terminal26U is connected to the connection wire29connecting the U-phase coil24U2and V-phase coil24V2adjacent in the circumferential direction.

A first V-phase fusing terminal26V is connected to the connection wire29connecting the V-phase coil24V1and W-phase coil24W1adjacent in the circumferential direction. A second V-phase fusing terminal26V is connected to the connection wire29connecting the V-phase coil24V2and W-phase coil24W2adjacent in the circumferential direction.

A first W-phase fusing terminal26W is connected to the connection wire29connecting the W-phase coil24W1and U-phase coil24U2adjacent in the circumferential direction. A second W-phase fusing terminal26W is connected to the connection wire29connecting the W-phase coil24W2and U-phase coil24U1adjacent in the circumferential direction.

The U-phase short-circuiting member27U short-circuits the U-phase power line25U and the two U-phase fusing terminals26U. The U-phase power line25U is located at one end of the U-phase short-circuiting member27U. The first U-phase fusing terminal26U is located at the other end of the U-phase short-circuiting member27U. The second U-phase fusing terminal26U is located in a middle portion of the U-phase short-circuiting member27U.

The V-phase short-circuiting member27V short-circuits the V-phase power line25V and the two V-phase fusing terminals26V. The V-phase power line25V is located at one end of the V-phase short-circuiting member27V. The first V-phase fusing terminal26V is located at the other end of the V-phase short-circuiting member27V. The second V-phase fusing terminal26V is located in a middle portion of the V-phase short-circuiting member27V.

The W-phase short-circuiting member27W short-circuits the W-phase power line W and the two W-phase fusing terminals26W. The W-phase power line25W is located at one end of the W-phase short-circuiting member27W. The first W-phase fusing terminal26W is located at the other end of the W-phase short-circuiting member27W. The second W-phase fusing terminal26W is located in a middle portion of the W-phase short-circuiting member27W.

As shown inFIG.7, the U-phase coil24U1, the V-phase coil24V1, and the W-phase coil24W1in one set are delta-connected to one another. The U-phase coil24U2, the V-phase coil24V2, and the W-phase coil24W2in one set are delta-connected to one another. These delta-connections are arranged in parallel.

When receiving a U-phase drive current, the U-phase power line25U feeds the U-phase drive current to each of the first and second U-phase fusing terminals26U through the U-phase short-circuiting member27U. When one U-phase coil24U1is magnetized to the N pole, the other U-phase coil24U2is magnetized to the S pole. The V-phase coil24V1adjacent to the U-phase coil24U1magnetized to the N pole is magnetized to the S pole. The V-phase coil24V2adjacent to the U-phase coil24U2magnetized to the S pole is magnetized to the N pole.

When receiving a V-phase drive current, the V-phase power line25V feeds the V-phase drive current to each of the first and second V-phase fusing terminals26V through the V-phase short-circuiting member27V. When one V-phase coil24V1is magnetized to the N pole, the other V-phase coil24V2is magnetized to the S pole. The W-phase coil24W1adjacent to the V-phase coil24V1magnetized to the N pole is magnetized to the S pole. The W-phase coil24W2adjacent to the V-phase coil24V2magnetized to the S pole is magnetized to the N pole.

When receiving a W-phase drive current, the W-phase power line25W feeds the W-phase drive current to each of the first and second W-phase fusing terminals26W through the W-phase short-circuiting member27W. When one W-phase coil24W1is magnetized to the N pole, the other W-phase coil24W2is magnetized to the S pole. The U-phase coil24U2adjacent to the W-phase coil24W1magnetized to the N pole is magnetized to the S pole. The U-phase coil24U1adjacent to the W-phase coil24W2magnetized to the S pole is magnetized to the N pole.

Sensor Board

The electric work machine1includes a sensor board40. The sensor board40includes magnetic sensors43for detecting rotation of the rotor301. The sensor board40is located frontward from the front insulator22. The sensor board40faces the front insulator22. The sensor board40includes a plate41, screw bosses42, the magnetic sensors43, and signal lines44.

The plate41is annular. Four screw bosses42protrude radially outward from the peripheral edge of the plate41.

The magnetic sensors43detect rotation of the rotor301. In the present embodiment, three magnetic sensors43are supported on the plate41. The magnetic sensors43each include a Hall device.

The magnetic sensors43output detection signals to the controller9through the signal lines44. The controller9provides a drive current to the multiple coils24based on the detection signals from the magnetic sensors43.

Fastening of Insulating Member, Sensor Board, and Front Insulator

The insulating member28supporting the short-circuiting members27, the sensor board40, and the front insulator22are fastened together with four screws18. The insulating member28, the sensor board40, and the front insulator22are fastened with the screws18to allow the signal lines44and at least parts of the power lines25to be aligned with each other in the circumferential direction.

Each screw boss28B on the insulating member28has an opening28D for receiving a middle portion of the corresponding screw18. Each screw boss42on the sensor board40has an opening45for receiving a middle portion of the corresponding screw18. The front insulator22has four threaded holes22D in its front surface. With the middle portion of each screw18received in the corresponding opening28D and opening45, the distal end of the screw18is fastened into the corresponding threaded hole22D. The insulating member28, the sensor board40, and the front insulator22are thus fastened with the screws18.

Rotor

FIG.8is a left side view of the rotor301in the present embodiment.FIG.9is a front view of the rotor301in the present embodiment.

As shown inFIGS.2to5,8, and9, the rotor301includes a rotor core31, a rotor shaft32, and permanent magnets33. The rotor301rotates about the rotation axis AX.

The rotor core31includes multiple steel plates stacked on one another. The steel plates are metal plates formed from iron as a main component. The rotor core31surrounds the rotation axis AX.

The rotor core31has a front end31F and a rear end31R. The front end31F is a first end of the rotor core31in the axial direction. The rear end31R is a second end of the rotor core31opposite to the first end in the axial direction.

The rotor shaft32extends in the axial direction. The rotor shaft32is located inward from the rotor core31. The rotor core31is fixed to the rotor shaft32. The rotor shaft32has a front portion protruding frontward from the front end31F of the rotor core31. The rotor shaft32has a rear portion protruding rearward from the rear end31R of the rotor core31. The rotor shaft32has the front portion rotatably supported by a front bearing (not shown). The rotor shaft32has the rear portion rotatably supported by a rear bearing (not shown). The rotor shaft32has its front end connected to the reducer described above.

The permanent magnets33are held by the rotor core31. The permanent magnets33in the present embodiment are located inside the rotor core31. The motor601is an interior permanent magnet (IPM) motor. In the present embodiment, four permanent magnets33surround the rotation axis AX. The permanent magnets33are fixed to the rotor core31.

The permanent magnets33are neodymium-iron-boron magnets. Each permanent magnet33has remanence of 1.0 to 1.5 T inclusive.

The sensor board40is located frontward from the rotor core31. As shown inFIG.8, the plate41in the sensor board40surrounds the front portion of the rotor shaft32. The magnetic sensors43are supported on the plate41. The magnetic sensors43face the front end31F of the rotor core31. The magnetic sensors43facing the front end31F of the rotor core31detect rotation of the rotor301. The magnetic sensors43detect the magnetic flux of the permanent magnets33to detect the position of the rotor301in the rotation direction.

The fan7is located rearward from the rotor core31. The fan7is fixed to the rear portion of the rotor shaft32. The fan7at least partially faces the rear end31R of the rotor core31. As the rotor shaft32rotates, the fan7rotates together with the rotor shaft32.

The rotor core31in the present embodiment includes a first core311and a second core312. The first core311has the front end31F. The second core312has the rear end31R. The second core312is adjacent to the first core311in the axial direction. The second core312is located rearward from the first core311.

FIG.10is a left view of the rotor core31in the present embodiment. As shown inFIG.10, the first core311includes multiple first steel plates35stacked on one another. The first steel plates35are stacked in the axial direction. The stacked first steel plates35are joined together by clinching to form the first core311.

The second core312includes multiple second steel plates36stacked on one another. The second steel plates36are stacked in the axial direction. The stacked second steel plates36are joined together by clinching to form the second core312.

The first core311and the second core312are joined to form the rotor core31. The stacked first steel plates35and the stacked second steel plates36may be joined together by clinching to form the rotor core31.

The first steel plates35each have an equal thickness T1. The second steel plates36each have an equal thickness T2. The thickness T1of each first steel plate35is equal to the thickness T2of each second steel plate36. The thickness T1of each first steel plate35refers to the axial dimension of each first steel plate35. The thickness T2of each second steel plate36refers to the axial dimension of each second steel plate36.

The thickness T1of each first steel plate35and the thickness T2of each second steel plate36are, for example, 0.30 to 0.40 mm inclusive. In the present embodiment, the thickness T1of each first steel plate35and the thickness T2of each second steel plate36are 0.35 mm.

In the axial direction, the first core311has a dimension L1smaller than a dimension L2of the second core312. The dimension L1of the first core311is, for example, 1.0 to 2.0 mm inclusive. The dimension L2of the second core312is, for example, greater than or equal to 3.0 mm.

The first steel plates35each have an equal outer shape. The first steel plates35each have an equal diameter. The second steel plates36each have an equal outer shape. The second steel plates36each have an equal diameter. The first steel plate35and the second steel plate36are equal in outer shape. The first steel plate35and the second steel plate36are equal in diameter.

The outer shape of the first steel plate35refers to the shape of the outer edge of the first steel plate35in a plane orthogonal to the rotation axis AX. The outer shape of the second steel plate36refers to the shape of the outer edge of the second steel plate36in a plane orthogonal to the rotation axis AX. The diameter of the first steel plate35refers to the maximum diameter of the first steel plate35. The diameter of the second steel plate36refers to the maximum diameter of the second steel plate36.

FIG.11is an exploded perspective view of the rotor core31and the permanent magnets33in the present embodiment as viewed from the rear.FIG.12is an exploded perspective view of the rotor core31and the permanent magnets33in the present embodiment as viewed from the front.

As shown inFIGS.10to12, the first core311surrounds the rotation axis AX. The second core312surrounds the rotation axis AX.

The first core311has a front surface311F, a rear surface311R, an outer surface311S, and an inner surface311T. The front surface311F is substantially annular. The rear surface311R is substantially annular. The outer surface311S connects the outer edge of the front surface311F and the outer edge of the rear surface311R. The inner surface311T connects the inner edge of the front surface311F and the inner edge of the rear surface311R. The first core311has an opening37in its center. The opening37extends through the front surface311F and the rear surface311R of the first core311in the axial direction. The inner surface311T of the first core311defines the inner surface of the opening37. The front end31F of the rotor core31includes the front surface311F of the first core311.

The second core312has a front surface312F, a rear surface312R, an outer surface312S, and an inner surface312T. The front surface312F is substantially annular. The rear surface312R is substantially annular. The outer surface312S connects the outer edge of the front surface312F and the outer edge of the rear surface312R. The inner surface312T connects the inner edge of the front surface312F and the inner edge of the rear surface312R. The second core312has an opening38in its center. The opening38extends through the front surface312F and the rear surface312R of the second core312in the axial direction. The inner surface312T of the second core312defines the inner surface of the opening38. The rear end31R of the rotor core31includes the rear surface312R of the second core312.

The rotation axis AX extends through the center of the first core311. The rotation axis AX extends through the center of the second core312. In the radial direction, a distance R1from the rotation axis AX to the outer surface311S of the first core311corresponds to the radius of the first core311. In the radial direction, a distance R2from the rotation axis AX to the outer surface312S of the second core312corresponds to the radius of the second core312. The distance R1is equal to the distance R2.

The distance R1and the distance R2are, for example, 15 to 20 mm inclusive. In the present embodiment, the distance R1and the distance R2are 18 mm.

The first core311and the second core312are equal in outer shape. The outer shape of the first core311refers to the shape of the outer edge of the first core311in a plane orthogonal to the rotation axis AX. The outer shape of the second core312refers to the shape of the outer edge of the second core312in a plane orthogonal to the rotation axis AX.

The first core311has recesses39A on the outer surface311S. Each recess39A extends in the axial direction. The recess39A has its front end connecting to the front surface311F of the first core311. The recess39A has its rear end connecting to the rear surface311R of the first core311. Multiple recesses39A are located on the outer surface311S. The multiple (four in the present embodiment) recesses39A are located at equal intervals in the circumferential direction about the rotation axis AX.

The second core312has recesses39B on the outer surface312S. Each recess39B extends in the axial direction. The recess39B has its front end connecting to the front surface312F of the second core312. The recess39B has its rear end connecting to the rear surface312R of the second core312. Multiple recesses39B are located on the outer surface312S. The multiple (four in the present embodiment) recesses39B are located at equal intervals in the circumferential direction about the rotation axis AX.

The recesses39A and39B reduce noise resulting from rotation of the rotor core31. Either or both of the recesses39A and the recesses39B may be eliminated.

The first core311and the second core312are connected to each other with the rear surface311R of the first core311in contact with the front surface312F of the second core312. The first core311and the second core312are connected to each other with the multiple recesses39A connected to the corresponding recesses39B.

The first core311has multiple (four in the present embodiment) first slots51. The multiple (four in the present embodiment) first slots51are located at intervals in the circumferential direction. The second core312has multiple second slots52. The multiple second slots52are located at intervals in the circumferential direction. The first slots51and the second slots52are equal in number.

The first slots51are located at intervals in the circumferential direction about the rotation axis AX. The first slots51extend through the front surface311F and the rear surface311R of the first core311.

The second slots52are located at intervals about the rotation axis AX. The second slots52extend through the front surface312F and the rear surface312R of the second core312.

The permanent magnets33are received in the respective first slots51and the respective second slots52. Multiple (four in the present embodiment) permanent magnets33surround the rotation axis AX. Each permanent magnet33is a rectangular plate elongated in the axial direction.

Each permanent magnet33has an inner surface33A, an outer surface33B, a front surface33C, a rear surface33D, a first side surface33E, and a second side surface33F. The inner surface33A faces radially inward. The outer surface33B faces radially outward. The front surface33C faces frontward. The rear surface33D faces rearward. The first side surface33E faces in the first circumferential direction. The second side surface33F faces in the second circumferential direction.

The first core311and the second core312are connected to each other with each first slot51at least partially overlapping the corresponding second slot52. Each first slot51and the corresponding second slot52at least partially overlapping the first slot define a single magnet slot50. In the present embodiment, four magnet slots50are located in the rotor core31. The magnet slots50each receive a single permanent magnet33.

FIG.13is a front view of the rotor core31in the present embodiment. As shown inFIG.13, the first slots51are located at equal intervals in the circumferential direction. The first slots51are equal in shape in a plane orthogonal to the rotation axis AX. The first slots51are equal in dimension in a plane orthogonal to the rotation axis AX.

The first core311includes first portions61each located between first slots51adjacent in the circumferential direction. In the circumferential direction, each first portion61has a dimension W1.

Multiple first portions61are located at equal intervals in the circumferential direction. The first portions61each have an equal dimension W1.

In the radial direction, a distance C1refers to the distance from the rotation axis AX to the first portion61. The rotation axis AX has an equal distance C1to each of the first portions61.

FIG.14is a rear view of the rotor core31in the present embodiment. As shown inFIG.14, the second slots52are located at equal intervals in the circumferential direction. The second slots52are equal in shape in a plane orthogonal to the rotation axis AX. The second slots52are equal in dimension in a plane orthogonal to the rotation axis AX.

The second core312includes second portions62each located between second slots52adjacent in the circumferential direction. In the circumferential direction, each second portion62has a dimension W2.

Multiple second portions62are located at equal intervals in the circumferential direction. The second portions62each have an equal dimension W2.

In the radial direction, a distance C2refers to the distance from the rotation axis AX to the second portion62. The rotation axis AX has an equal distance C2to each of the second portions62.

As shown inFIGS.13and14, the first portions61and the second portions62are equal in number. In present embodiment, four first portions61and four second portions62are located in the circumferential direction.

In the circumferential direction, the first portion61has the dimension W1smaller than the dimension W2of the second portion62.

The first portion61has the dimension W1of 0.2 to 1.0 mm inclusive. The second portion62has the dimension W2of 2.0 to 10.0 mm inclusive.

The rotation axis AX has the distance C1to each first portion61being equal to the distance C2from the rotation axis AC to each second portion62.

As shown inFIG.13, the surface of each permanent magnet33in the corresponding first slot51and at least a part of the inner surface of the first slot51define a first space71between them. The first space71in the present embodiment faces the first side surface33E or the second side surface33F. The first space71receives a first resin portion73.

As shown inFIG.14, the surface of each permanent magnet33in the corresponding second slot52and at least a part of the inner surface of the second slot52define a second space72between them. The second space72in the present embodiment faces the first side surface33E or the second side surface33F. The second space72receives a second resin portion74.

The permanent magnets33include first permanent magnets331and second permanent magnets332. The first permanent magnets331each have the S pole facing radially outward. The second permanent magnets332each have the N pole facing radially outward. The first permanent magnets331and the second permanent magnets332are arranged alternately in the circumferential direction. The four permanent magnets33surround the rotation axis AX. The permanent magnets33include two first permanent magnets331and two second permanent magnets332.

FIG.15is a cross-sectional view of the first core311in the present embodiment, taken along line A-A inFIG.10as viewed in the direction indicated by arrows.FIG.16is a partially enlarged cross-sectional view of the first core311in the present embodiment. As shown inFIGS.15and16, the inner surface of each first slot51includes a first support surface51A, a second support surface51B, a third support surface51E, a fourth support surface51F, a first extension surface51G, a first facing surface51H, a first connecting surface51I, a second extension surface51J, a second facing surface51K, and a second connecting surface51L.

The first support surface51A faces radially outward. The first support surface51A is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The first support surface51A faces the inner surface33A of the permanent magnet33.

The second support surface51B faces radially inward. The second support surface51B is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The second support surface51B faces the outer surface33B of the permanent magnet33.

The third support surface51E faces in the second tangential direction. The third support surface51E connects to one end of the second support surface51B in the first tangential direction. The third support surface51E faces a radially outer portion of the first side surface33E of the permanent magnet33.

The fourth support surface51F faces in the first tangential direction. The fourth support surface51F connects to the other end of the second support surface51B in the second tangential direction. The fourth support surface51F faces a radially outer portion of the second side surface33F of the permanent magnet33.

The permanent magnet33is supported by the first support surface51A, the second support surface51B, the third support surface51E, and the fourth support surface51F.

The first extension surface51G faces radially outward. The first extension surface51G extends in the first tangential direction from one end of the first support surface51A. The first facing surface51H faces radially inward. The first facing surface51H faces at least a portion of the first extension surface51G. The first facing surface51H connects to a radially inner end of the third support surface51E.

The first connecting surface51I connects an end of the first extension surface51G in the first tangential direction and an end of the first facing surface51H in the first tangential direction.

The second extension surface51J faces radially outward. The second extension surface51J extends in the second tangential direction from the other end of the first support surface51A.

The second facing surface51K faces radially inward. The second facing surface51K faces at least a portion of the second extension surface51J. The second facing surface51K connects to a radially inner end of the fourth support surface51F.

The second connecting surface51L connects an end of the second extension surface51J in the second tangential direction and an end of the second facing surface51K in the second tangential direction.

In each first slot51, one first space71is defined by the first side surface33E of the permanent magnet33, the first extension surface51G, the first facing surface51H, and the first connecting surface51I. The other first space71is defined by the second side surface33F of the permanent magnet33, the second extension surface51J, the second facing surface51K, and the second connecting surface51L.

The first space71receiving the first resin portion73reduces movement of the permanent magnet33inside the magnet slot50. The first resin portion73may be located between the outer surface33B of the permanent magnet33and the second support surface51B of the first slot51. This firmly fixes the permanent magnet33to the rotor core31.

FIG.17is a cross-sectional view of the second core312in the present embodiment, taken along line B-B inFIG.10as viewed in the direction indicated by arrows.FIG.18is a partially enlarged cross-sectional view of the second core312in the present embodiment.

As shown inFIGS.17and18, the inner surface of each second slot52includes a fifth support surface52A, a sixth support surface52B, a seventh support surface52E, an eighth support surface52F, a third extension surface52H, a third facing surface52G, a third connecting surface52I, a fourth extension surface52K, a fourth facing surface52J, and a fourth connecting surface52L.

The fifth support surface52A faces radially outward. The fifth support surface52A is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The fifth support surface52A faces the inner surface33A of the permanent magnet33.

The sixth support surface52B faces radially inward. The sixth support surface52B is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The sixth support surface52B faces the outer surface33B of the permanent magnet33.

The seventh support surface52E faces in the second tangential direction. The seventh support surface52E connects to one end of the fifth support surface52A in the first tangential direction. The seventh support surface52E faces a radially inner portion of the first side surface33E of the permanent magnet33.

The eighth support surface52F faces in the first tangential direction. The eighth support surface52F connects to the other end of the fifth support surface52A in the second tangential direction. The eighth support surface52F faces a radially inner portion of the second side surface33F of the permanent magnet33.

The permanent magnet33is supported by the fifth support surface52A, the sixth support surface52B, the seventh support surface52E, and the eighth support surface52F.

The third extension surface52H faces radially inward. The third extension surface52H extends in the first tangential direction from one end of the sixth support surface52B.

The third facing surface52G faces radially outward. The third facing surface52G faces at least a portion of the third extension surface52H. The third facing surface52G connects to a radially outer end of the seventh support surface52E.

The third connecting surface52I connects an end of the third extension surface52H in the first tangential direction and an end of the third facing surface52G in the first tangential direction.

The fourth extension surface52K faces radially inward. The fourth extension surface52K extends in the second tangential direction from the other end of the sixth support surface52B.

The fourth facing surface52J faces radially outward. The fourth facing surface52J faces at least a portion of the fourth extension surface52K. The fourth facing surface52J connects to a radially outer end of the eighth support surface52F.

The fourth connecting surface52L connects an end of the fourth extension surface52K in the second tangential direction and an end of the fourth facing surface52J in the second tangential direction.

In each second slot52, one second space72is defined by the first side surface33E of the permanent magnet33, the third extension surface52H, the third facing surface52G, and the third connecting surface52I. The other second space72is defined by the second side surface33F of the permanent magnet33, the fourth extension surface52K, the fourth facing surface52J, and the fourth connecting surface52L.

The second space72receiving the second resin portion74reduces movement of the permanent magnet33inside the magnet slot50. The second resin portion74may be located between the outer surface33B of the permanent magnet33and the sixth support surface52B of the second slot52. This firmly fixes the permanent magnet33to the rotor core31.

In the tangential direction, the first slot51has a dimension E1greater than a dimension E2of the second slot52.

In the radial direction, the first slot51has a dimension H1equal to a dimension H2of the second slot52. The dimension H1refers to a radial distance between the first support surface51A and the second support surface51B. The dimension H2refers to a radial distance between the fifth support surface52A and the sixth support surface52B.

The first core311and the second core312are connected to each other with the center of each first slot51aligned with the center of the corresponding second slot52in the tangential or circumferential direction. The first core311and the second core312are also connected to each other with the center of each first slot51aligned with the center of the corresponding second slot52in the radial direction.

With the first core311and the second core312connected to each other, the first support surface51A connects to the fifth support surface52A, and the second support surface51B connects to the sixth support surface52B. The first support surface51A is flush with the fifth support surface52A. The second support surface51B is flush with the sixth support surface52B. The third support surface51E is located radially outward from the seventh support surface52E. The fourth support surface51F is located radially outward from the eighth support surface52F. With the first core311and the second core312connected to each other, the first space71at least partially overlap the second space72. The second space72is at least partially located radially outward from the first space71.

Operation

The operation of the motor601will now be described. In response to an operation on the trigger switch10, a drive current is supplied from the battery pack14to the coils24in the stator20through the controller9. This generates a rotating magnetic field in the stator20, and a magnetic flux flows to the rotor core31as indicated by arrow MF inFIGS.15and17. The rotating magnetic field generated in the stator20causes the rotor301to rotate about the rotation axis AX.

The motor601generates magnetic torque and reluctance torque. Magnetic torque refers to the torque generated by the attractive force or the repulsive force between the rotating magnetic field in the stator20and the permanent magnets33in the rotor301. Reluctance torque refers to the torque generated by the attractive force between the rotating magnetic field in the stator20and the rotor core31in the rotor301. The torque generated by the motor601is composite torque of the magnetic torque and the reluctance torque.

More permanent magnets33generate larger torque. Fewer permanent magnets33generate smaller torque. A larger magnetic flux path in the rotor core31generates larger reluctance torque. A smaller magnetic flux path in the rotor core31generates smaller reluctance torque.

As shown inFIGS.15and17, the first portions61and the second portions62define magnetic flux paths in the rotor core31. In the present embodiment, each second portion62has the dimension W2greater than the dimension W1of the first portion61. In other words, the magnetic flux path in the second core312is larger than the magnetic flux path in the first core311. The second core312generates larger reluctance torque than the first core311relative to the stator20.

The second core312includes the second portions62as the magnetic flux paths each having a greater dimension W2. The motor601can thus generate predetermined composite torque with fewer permanent magnets33. Fewer permanent magnets33reduce the production cost of the motor601.

The magnetic sensors43detect the rotation of the rotor301by detecting the switching of the magnetic poles between the first permanent magnets331and the second permanent magnets332as the rotor301rotates. In other words, the magnetic sensors43detect the direction of the magnetic field that changes in accordance with the rotation of the rotor301. The first permanent magnets331each have the S pole facing radially outward as described above. The second permanent magnets332each have the N pole facing radially outward.

As the rotor301rotates, the magnetic pole of the permanent magnet33at the shortest distance from the corresponding magnetic sensor43switches between the S pole of the first permanent magnet331and the N pole of the second permanent magnet332. The direction of the magnetic field switching from the S pole of the first permanent magnet331to the N pole of the second permanent magnet332is different from the direction of the magnetic field switching from the N pole of the second permanent magnet332to the S pole of the first permanent magnet331. The magnetic sensor43thus detects the direction of the magnetic field changing in accordance with the rotation of the rotor301to detect the switching of the magnetic poles (the S pole or the N pole) of the corresponding permanent magnet33as the rotor301rotates. The magnetic sensor43thus detects the rotation of the rotor301.

In the rotor core31including a larger magnetic flux path, the magnetic flux may leak from the rotor core31and may disable the magnetic sensors43from correctly detecting the switching of the magnetic poles of the permanent magnets33as the rotor301rotates. This may reduce the detection accuracy of the rotation of the rotor301.

In the present embodiment, the first portion61has the dimension W1smaller than the dimension W2of the second portion62. In other words, the first core311includes the magnetic flux path smaller than the magnetic flux path in the second core312. The first core311generates smaller reluctance torque than the second core312relative to the stator20.

The first core311includes the first portions61as the magnetic flux paths each having a smaller dimension W1. This reduces the magnetic flux leaking from the rotor core31. This allows the magnetic sensors43to be less susceptible to the magnetic flux leaking from the rotor core31. The magnetic sensors43can thus correctly detect the switching of the magnetic poles of the permanent magnets33as the rotor301rotates. The detection accuracy of the rotation of the rotor301is thus less likely to be reduced.

FIG.19is a graph showing the relationship between the size of the magnetic flux path in the rotor core31, the magnetic flux detected by the magnetic sensor43, and the rotation angle of the rotor301.FIG.19shows the magnetic flux detected by a single magnetic sensor43per rotation of the rotor301.

InFIG.19, line La represents the magnetic flux detected by the magnetic sensor43with the rotor core31including a smaller magnetic flux path. Line Lb represents the magnetic flux detected by the magnetic sensor43in the rotor core31including a larger magnetic flux path.

The magnetic sensor43detects the direction of the magnetic field that changes in accordance with the rotation of the rotor301. With the rotor core31including a larger magnetic flux path, as indicated by line Lb, when the magnetic pole of the permanent magnet33detected by the magnetic sensor43switches from the N pole to the S pole, a magnetic field may be generated in the direction opposite to the direction of the magnetic field resulting from the permanent magnet33, as indicated by arrows Vn, due to the magnetic flux leaking from the rotor core31. Similarly, when the magnetic pole of the permanent magnet33detected by the magnetic sensor43switches from the S pole to the N pole, a magnetic field may be generated in the direction opposite to the direction of the magnetic field resulting from the permanent magnet33, as indicated by arrows Vs, due to the magnetic flux leaking from the rotor core31. In other words, with the rotor core31including a larger magnetic flux path, the direction of the magnetic field changes, at a position of detection by the magnetic sensor43, the number of times greater than the number of permanent magnets33per rotation of the rotor301. The magnetic sensor43may not correctly detect the switching of the magnetic poles of the permanent magnet33. The position of detection by the magnetic sensor43includes a position facing the magnetic sensor43.

In the present embodiment, the dimension W1of the first portion61of the first core311is determined to cause the direction of the magnetic field to change, at a position of detection by the magnetic sensor43, the number of times equal to the number of permanent magnets33per rotation of the rotor301. Four permanent magnets33are used in the present embodiment. As indicated by line La, the dimension W1of the first portion61is determined to cause the direction of the magnetic field to change four times per rotation of the rotor301. In other words, the dimension W1of the first portion61is determined to cause no magnetic field to be generated in the direction opposite to the direction of the magnetic field resulting from the permanent magnet33. The detection accuracy of the rotation of the rotor301is thus less likely to be reduced.

As described above, the rotor core31in the present embodiment includes the first core311including the front end31F and the second core312adjacent to the first core311in the axial direction. The magnetic sensors43face the first core311. The first core311includes the first portions61located between the first slots51adjacent in the circumferential direction. The second core312includes the second portions62located between the second slots52adjacent in the circumferential direction. The first portions61define the magnetic flux paths in the first core311. The second portions62define the magnetic flux paths in the second core312. In the circumferential direction, the first portion61has the dimension W1smaller than the dimension W2of the second portion62. The first core311facing the magnetic sensors43includes smaller magnetic flux paths, reducing the magnetic flux leaking from the rotor core31to the magnetic sensors43. The magnetic sensors43can thus correctly detect the switching of the magnetic poles of the permanent magnets33per rotation of the rotor301. The detection accuracy of the rotation of the rotor301is thus less likely to be reduced.

The second portion62has the dimension W2greater than the dimension W1of the first portion61. The second core312with larger magnetic flux paths generates large reluctance torque. This reduces generation of insufficient reluctance torque. In some embodiments, the motor601may generate a predetermined level of composite torque with fewer permanent magnets33. The use of fewer permanent magnets33reduces the production cost of the motor601.

The multiple first portions61are located in the circumferential direction. The first portions61each have an equal dimension W1. The magnetic sensors43can thus correctly detect the switching of the magnetic poles of the permanent magnets33per rotation of the rotor301.

The multiple second portions62are located in the circumferential direction. The second portions62each have an equal dimension W2. The reluctance torque is thus generated uniformly per rotation of the rotor301.

Each magnetic sensor43detects the direction of the magnetic field that changes in accordance with the rotation of the rotor301. As described with reference toFIG.19, the dimension W1of the first portion61is determined to cause the direction of the magnetic field to change the number of times equal to the number of permanent magnets33per rotation of the rotor301. The magnetic sensors43can thus correctly detect the switching of the magnetic poles of the permanent magnets33as the rotor301rotates.

The first portion61has the dimension W1of 0.2 to 1.0 mm inclusive. This causes the direction of the magnetic field to change the number of times equal to the number of permanent magnets33per rotation of the rotor301. The permanent magnets33are neodymium-iron-boron magnets in the present embodiment. With the permanent magnet33having remanence of 1.0 to 1.5 T inclusive, the direction of the magnetic field may be more likely to change the number of times equal to the number of permanent magnets33per rotation of the rotor301when the dimension W1is 0.2 to 1.0 mm inclusive.

The second portion62has the dimension W2of 2.0 to 10.0 mm inclusive. This generates sufficient reluctance torque. The permanent magnets33are neodymium-iron-boron magnets in the present embodiment. With the permanent magnet33having remanence of 1.0 to 1.5 T inclusive, sufficient reluctance torque is likely to be generated when the dimension W2is 2.0 to 10.0 mm inclusive. A permanent magnet33formed from a material different from a neodymium-iron-boron magnet but having remanence greater than or equal to the remanence of the neodymium-iron-boron magnet may have the dimension W2of 2.0 to 10.0 mm inclusive. The permanent magnet33is then likely to generate sufficient reluctance torque.

The first slots51and the second slots52are equal in number. Each first slot51and the corresponding second slot52at least partially overlapping the first slot51define a single magnet slot50. The magnet slots50each receive a single permanent magnet33. This facilitates smooth placement of the permanent magnets33in the respective magnet slots50.

The first core311and the second core312are connected to each other with the center of each first slot51aligned with the center of the corresponding second slot52. This improves the weight balance of the rotor301and allows smooth rotation of the rotor301. This also facilitates smooth placement of the permanent magnets33in the respective magnet slots50.

In the radial direction, the first slot51has the dimension H1equal to the dimension H2of the second slot52. This stably positions the rectangular permanent magnets33elongated in the axial direction in the respective first slots51and the respective second slots52.

The surface of each permanent magnet33and at least a part of the inner surface of the first slot51define the first space71between them. The surface of each permanent magnet33and at least a part of the inner surface of the second slot52define the second space72between them. This reduces the likelihood of short-circuiting between the magnetic flux of the permanent magnets33and the magnetic flux passing through the rotor core31, as indicated by arrows MF inFIGS.15and17.

The first space71receives the first resin portion73. The second space72receives the second resin portion74. This reduces movement of the permanent magnet33inside the magnet slot50.

The first slots51are equal in shape and in dimension. The second slots52are equal in shape and in dimension. This improves the weight balance of the rotor301and allows smooth rotation of the rotor301.

In the axial direction, the first core311has the dimension L1smaller than the dimension L2of the second core312. The second core312having the dimension L2smaller than the dimension L1of the first core311may generate insufficient reluctance torque. The first core311having a smaller dimension L1can reduce generation of a magnetic field in a direction opposite to the direction of the magnetic field resulting from the permanent magnet33. The first core311having the dimension L1smaller than the dimension L2of the second core312can reduce a decrease in the detection accuracy of the rotation of the rotor301while avoiding generation of insufficient reluctance torque.

The first core311has the dimension L1of 1.0 to 2.0 mm inclusive. The first core311having the dimension L1less than 1.0 mm cannot sufficiently reduce generation of a magnetic field in a direction opposite to the direction of the magnetic field resulting from the permanent magnets33. The first core311having the dimension L1greater than 2.0 mm cannot effectively reduce generation of a magnetic field in a direction opposite to the direction of the magnetic field resulting from the permanent magnets33. The first core311having the dimension L1of 1.0 to 2.0 mm inclusive can reduce a decrease in the detection accuracy of the rotation of the rotor301while avoiding generation of insufficient reluctance torque.

In the radial direction, the rotation axis AX has an equal distance C1to each of the first portions61. In the radial direction, the rotation axis AX has an equal distance C2to each of the second portions62. This improves the weight balance of the rotor301and allows smooth rotation of the rotor301. The rotation axis AX has an equal distance C1to each of the first portions61. This reduces variation in signals detected by the magnetic sensors43.

In the radial direction, the rotation axis AX has the distance C1to each first portion61being equal to the distance C2from the rotation axis AX to each second portion62. This improves the weight balance of the rotor301and allows smooth rotation of the rotor301.

In the radial direction, the distance R1from the rotation axis AX to the outer surface311S of the first core311is equal to the distance R2from the rotation axis AX to the outer surface312S of the second core312. This allows the rotor core31located inward from the stator20to rotate smoothly.

The first core311and the second core312are equal in outer shape. This allows the rotor core31located inward from the stator20to rotate smoothly.

The first core311includes the multiple first steel plates35stacked on one another. The second core312includes the multiple second steel plates36stacked on one another. The first steel plate35and the second steel plate36are equal in shape and have the thickness T1and the thickness T2equal to each other. This reduces the production cost of the rotor core31.

Other Embodiments

FIG.20is a perspective view of a rotor301B in another example of the present embodiment as viewed from the rear. As shown inFIG.20, the rotor core31includes the first core311, the second core312, and a third core313. The first core311includes the front end31F of the rotor core31. The third core313includes the rear end31R of the rotor core31. In the axial direction, the second core312is located between the first core311and the third core313.

The third core313and the first core311are equal in shape. The third core313and the first core311are equal in dimension. In other words, the first core311and the third core313are identical.

In the example shown inFIG.20, for example, the rotor core31may be axially reversed and fixed to the rotor shaft32to produce the same rotor301. The productivity of the rotor301is less likely to decrease.

Second Embodiment

A second embodiment will now be described. The same or corresponding components as those in the above embodiment are given the same reference numerals herein, and will be described briefly or will not be described.

Electric Work Machine

FIG.21is a perspective view of an electric work machine101according to the present embodiment. The electric work machine101according to the present embodiment is a chain saw as an example of outdoor power equipment.

The electric work machine101includes a housing102, a hand guard103, a first grip104, a battery mount105, a motor602, a trigger switch106, a trigger lock lever107, a guide bar108, and a saw chain109.

The housing102is formed from a synthetic resin. The housing102includes a motor compartment110, a battery holder111, and a second grip112.

The motor compartment110accommodates the motor602. The battery holder111is connected to the motor compartment110. The battery holder111includes the battery mount105to which the battery pack14is attached. The battery holder111accommodates the controller9. The second grip112is connected to the battery holder111. The trigger switch106and the trigger lock lever107are located in the second grip112. The trigger lock lever107is operable to allow an operation of the trigger switch106.

The guide bar108is supported by the housing102. The guide bar108is a plate. The saw chain109includes multiple cutters that are connected to one another. The saw chain109is located along the peripheral edge of the guide bar108. In response to an operation on the trigger switch106, the motor602is driven. The motor602and the saw chain109are connected with a power transmission (not shown) including a sprocket. The motor602is driven, and the saw chain109moves around the peripheral edge of the guide bar108.

The sprocket is directly fixed to a rotor shaft32in the motor602. More specifically, the motor602in the present embodiment drives the saw chain109with a direct drive system. A reducer is not located between the motor602and the sprocket. A reducer may be included. The reducer allows the saw chain109to drive with higher torque.

The first grip104is formed from a synthetic resin. The first grip104is grippable by the operator of the electric work machine101. The first grip104is a pipe. The first grip104connects to the battery holder111. The first grip104has one end and the other end both connected to a surface of the battery holder111.

Rotor

FIG.22is a perspective view of a rotor302in the present embodiment as viewed from the rear.FIG.23is a perspective view of the rotor302in the present embodiment as viewed from the front.FIG.24is a perspective view of a rotor core31in the present embodiment as viewed from the front.FIG.25is a front view of the rotor core31in the present embodiment.FIG.26is a rear view of the rotor core31in the present embodiment.FIG.27is a cross-sectional view of a first core311in the present embodiment, taken along line C-C inFIG.24as viewed in the direction indicated by arrows.FIG.28is a partially enlarged cross-sectional view of the first core311in the present embodiment.FIG.29is a cross-sectional view of a second core312in the present embodiment, taken along line D-D inFIG.24as viewed in the direction indicated by arrows.FIG.30is a partially enlarged cross-sectional view of the first core311in the present embodiment.

As shown inFIGS.22to30, the rotor302includes the rotor core31, the rotor shaft32, and permanent magnets33.

The rotor core31has a front end31F and a rear end31R. As in the above embodiment, magnetic sensors43face the front end31F of the rotor core31.

The permanent magnets33are held by the rotor core31. In the present embodiment, eight permanent magnets33surround the rotation axis AX.

The rotor core31includes the first core311and the second core312. The first core311has the front end31F. The second core312is located rearward from the first core311. The first core311is substantially cylindrical. The second core312is substantially cylindrical. The first core311and the second core312are equal in outer shape.

The first core311has multiple (eight in the present embodiment) first slots51located at intervals in the circumferential direction. The second core312has multiple (eight in the present embodiment) second slots52located at intervals in the circumferential direction. The first slots51and the second slots52are equal in number.

The multiple first slots51are located at equal intervals in the circumferential direction. The first slots51are equal in shape in a plane orthogonal to the rotation axis AX. The first slots51are equal in dimension in a plane orthogonal to the rotation axis AX.

The multiple second slots52are located at equal intervals in the circumferential direction. The second slots52are equal in shape in a plane orthogonal to the rotation axis AX. The second slots52are equal in dimension in a plane orthogonal to the rotation axis AX.

The permanent magnets33are received in the respective first slots51and the respective second slots52. Multiple (eight in the present embodiment) permanent magnets33surround the rotation axis AX. Each permanent magnet33is a rectangular plate elongated in the axial direction.

The first core311and the second core312are connected to each other with each first slot51at least partially overlapping the corresponding second slot52. Each first slot51and the corresponding second slot52at least partially overlapping the first slot51define a single magnet slot50. In the present embodiment, eight magnet slots50are located in the rotor core31. The magnet slots50each receive a single permanent magnet33.

The first core311includes first portions61each located between first slots51adjacent in the circumferential direction.

Multiple first portions61are located at equal intervals in the circumferential direction. In the circumferential direction, the multiple first portions61each have an equal dimension W1.

In the radial direction, the rotation axis AX has an equal distance C1to each of the first portions61.

The second core312includes second portions62each located between second slots52adjacent in the circumferential direction.

Multiple second portions62are located at equal intervals in the circumferential direction. In the circumferential direction, the multiple second portions62each have an equal dimension W2.

In the radial direction, the rotation axis AX has an equal distance C2to each of the second portions62.

The first portions61and the second portions62are equal in number. In present embodiment, eight first portions61are located in the circumferential direction. Eight second portions62are located in the circumferential direction.

In the circumferential direction, the first portion61has the dimension W1smaller than the dimension W2of the second portion62.

The first portion61has the dimension W1of 0.2 to 1.0 mm inclusive. The second portion62has the dimension W2of 2.0 to 10.0 mm inclusive.

In the radial direction, the rotation axis AX has the distance C1to each first portion61being equal to the distance C2from the rotation axis AC to each second portion62.

The surface of each permanent magnet33in the corresponding first slot51and at least a part of the inner surface of the first slot51define a first space71between them. The first space71receives a first resin portion73.

The surface of each permanent magnet33in the corresponding second slot52and at least a part of the inner surface of the second slot52define a second space72between them. The second space72receives a second resin portion74.

The permanent magnets33include first permanent magnets331and second permanent magnets332. The first permanent magnets331each have the S pole facing radially outward. The second permanent magnets332each have the N pole facing radially outward. The first permanent magnets331and the second permanent magnets332are arranged alternately in the circumferential direction. The permanent magnets33include four first permanent magnets331and four second permanent magnets332.

In the present embodiment, the rotor core31has through-holes19. The through-holes19extend through a front surface311F of the first core311and a rear surface312R of the second core312. The through-holes19are located between an opening37and an outer surface311S of the first core311in the radial direction. The through-holes19are located between an opening38and an outer surface312S of the second core312in the radial direction. Four through-holes19are located about the rotation axis AX. The through-holes19are arc-shaped in a plane orthogonal to the rotation axis AX. The through-holes19reduce the weight of the rotor core31.

As shown inFIG.28, the inner surface of each first slot51includes a first support surface51A, a second support surface51B, a third support surface51E, a fourth support surface51F, a first extension surface51G, a first facing surface51H, a first connecting surface51I, a second extension surface51J, a second facing surface51K, and a second connecting surface51L.

The first support surface51A faces radially outward. The first support surface51A is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The first support surface51A faces the inner surface33A of the permanent magnet33.

The second support surface51B faces radially inward. The second support surface51B is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The second support surface51B faces the outer surface33B of the permanent magnet33.

The third support surface51E faces in the second tangential direction. The third support surface51E connects to one end of the second support surface51B in the first tangential direction. The third support surface51E faces a radially inner portion of the first side surface33E of the permanent magnet33.

The fourth support surface51F faces in the first tangential direction. The fourth support surface51F connects to the other end of the second support surface51B in the second tangential direction. The fourth support surface51F faces a radially inner portion of the second side surface33F of the permanent magnet33.

The permanent magnet33is supported by the first support surface51A, the second support surface51B, the third support surface51E, and the fourth support surface51F.

The first extension surface51G faces radially inward. The first extension surface51G extends in the first tangential direction from one end of the second support surface51B. The first facing surface51H faces radially outward. The first facing surface51H faces at least a portion of the first extension surface51G. The first facing surface51H connects to a radially outer end of the third support surface51E.

The first connecting surface51I connects an end of the first extension surface51G in the first tangential direction and an end of the first facing surface51H in the first tangential direction.

The second extension surface51J faces radially inward. The second extension surface51J extends in the second tangential direction from the other end of the second support surface51B.

The second facing surface51K faces radially outward. The second facing surface51K faces at least a portion of the second extension surface51J. The second facing surface51K connects to a radially outer end of the fourth support surface51F.

The second connecting surface51L connects an end of the second extension surface51J in the second tangential direction and an end of the second facing surface51K in the second tangential direction.

In each first slot51, one first space71is defined by the first side surface33E of the permanent magnet33, the first extension surface51G, the first facing surface51H, and the first connecting surface51I. The other first space71is defined by the second side surface33F of the permanent magnet33, the second extension surface51J, the second facing surface51K, and the second connecting surface51L.

The first space71receiving the first resin portion73reduces movement of the permanent magnet33inside the magnet slot50. The first resin portion73may be located between the outer surface33B of the permanent magnet33and the second support surface51B of the first slot51. This firmly fixes the permanent magnet33to the rotor core31. The first resin portion73may be located between the first side surface33E and the third support surface51E. The first resin portion73may be located between the second side surface33F and the fourth support surface51F.

As shown inFIG.30, the inner surface of each second slot52includes a fifth support surface52A, a sixth support surface52B, a seventh support surface52E, an eighth support surface52F, a third extension surface52H, a third facing surface52G, a third connecting surface52I, a fourth extension surface52K, a fourth facing surface52J, and a fourth connecting surface52L.

The fifth support surface52A faces radially outward. The fifth support surface52A is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The fifth support surface52A faces the inner surface33A of the permanent magnet33.

The sixth support surface52B faces radially inward. The sixth support surface52B is parallel to a tangent of an imaginary circle with the rotation axis AX at the center. The sixth support surface52B faces the outer surface33B of the permanent magnet33.

The seventh support surface52E faces in the second tangential direction. The seventh support surface52E connects to one end of the fifth support surface52A in the first tangential direction. The seventh support surface52E faces a radially inner portion of the first side surface33E of the permanent magnet33.

The eighth support surface52F faces in the first tangential direction. The eighth support surface52F connects to the other end of the fifth support surface52A in the second tangential direction. The eighth support surface52F faces a radially inner portion of the second side surface33F of the permanent magnet33.

The permanent magnet33is supported by the fifth support surface52A, the sixth support surface52B, the seventh support surface52E, and the eighth support surface52F.

The third extension surface52H faces radially inward. The third extension surface52H extends in the first tangential direction from one end of the sixth support surface52B. The third facing surface52G faces radially outward. The third facing surface52G faces at least a portion of the third extension surface52H. The third facing surface52G connects to a radially outer end of the seventh support surface52E.

The third connecting surface52I connects an end of the third extension surface52H in the first tangential direction and an end of the third facing surface52G in the first tangential direction.

The fourth extension surface52K faces radially inward. The fourth extension surface52K extends in the second tangential direction from the other end of the sixth support surface52B.

The fourth facing surface52J faces radially outward. The fourth facing surface52J faces at least a portion of the fourth extension surface52K. The fourth facing surface52J connects to a radially outer end of the eighth support surface52F.

The fourth connecting surface52L connects an end of the fourth extension surface52K in the second tangential direction and an end of the fourth facing surface52J in the second tangential direction.

In each second slot52, one second space72is defined by the first side surface33E of the permanent magnet33, the third extension surface52H, the third facing surface52G, and the third connecting surface52I. The other second space72is defined by the second side surface33F of the permanent magnet33, the fourth extension surface52K, the fourth facing surface52J, and the fourth connecting surface52L.

The second space72receiving the second resin portion74reduces movement of the permanent magnet33inside the magnet slot50. The second resin portion74may be located between the outer surface33B of the permanent magnet33and the sixth support surface52B of the second slot52. This firmly fixes the permanent magnet33to the rotor core31. The second resin portion74may be located between the first side surface33E and the seventh support surface52E. The first resin portion73may be located between the second side surface33F and the eighth support surface52F.

In the tangential direction, the first slot51has a dimension E1greater than a dimension E2of the second slot52.

In the radial direction, the first slot51has a dimension H1equal to a dimension H2of the second slot52.

The first core311and the second core312are connected to each other with the center of each first slot51aligned with the center of the corresponding second slot52in the tangential or circumferential direction. The first core311and the second core312are connected to each other with the center of each first slot51aligned with the center of the corresponding second slot52in the radial direction.

With the first core311and the second core312connected to each other, the first support surface51A connects to the fifth support surface52A, and the second support surface51B connects to the sixth support surface52B. The first support surface51A is flush with the fifth support surface52A. The second support surface51B is flush with the sixth support surface52B.

With the first core311and the second core312connected to each other, the third support surface51E connects to the seventh support surface52E, and the fourth support surface51F connects to the eighth support surface52F. The third support surface51E is flush with the seventh support surface52E. The fourth support surface51F is flush with the eighth support surface52F. With the first core311and the second core312connected to each other, the first space71at least partially overlap the second space72.

As described above, the rotor core31supporting the eight permanent magnets33reduces a decrease in the detection accuracy of the rotation of the rotor301while avoiding generation of insufficient reluctance torque.

Third Embodiment

A third embodiment will now be described. The same or corresponding components as those in the above embodiment are given the same reference numerals herein, and will be described briefly or will not be described.

Use of Common Stator

FIG.31is a schematic diagram describing the relationship between a stator200and a rotor300in the present embodiment. The stator200is the same as the stator20in the first embodiment described above. The stator200includes a stator core21with six teeth21T and six coils24wound around each of the six teeth21T in the stator core21.

As shown inFIG.31, the stator200can be combined with one of multiple types of rotors300. The stator that can be combined with the rotor refers to the stator that allows the rotor to rotate relative to the stator in response to magnetization of the coils (teeth) included in the stator. In the example shown inFIG.31, the rotor300that can be combined with the stator200includes a first rotor3001and a second rotor3002.

The first rotor3001is the same as the rotor301in the first embodiment described above. The first rotor3001includes four magnet slots50and four permanent magnets33located in each of the four magnet slots50. The second rotor3002is the same as the rotor302in the second embodiment described above. The second rotor3002includes eight magnet slots50and eight permanent magnets33located in each of the eight magnet slots50.

The first rotor3001and the second rotor3002are equal in outer diameter. The first rotor3001has an outer diameter corresponding to the outer diameter of the rotor core31in the first rotor3001. The second rotor3002has an outer diameter corresponding to the outer diameter of the rotor core31in the second rotor3002.

In the axial direction, the first rotor3001and the second rotor3002are equal in dimension. The first rotor3001has an axial dimension corresponding to the axial dimension of the rotor core31in the first rotor3001. The second rotor3002has an axial dimension corresponding to the axial dimension of the rotor core31in the second rotor3002.

The first rotor3001and the second rotor3002have different numbers of poles. The first rotor3001has four poles. The second rotor3002has eight poles. The first rotor3001can be combined with the stator200. The second rotor3002can also be combined with the stator200. The first rotor3001located inward from the stator200is rotatable under the rotating magnetic field of the stator200. The second rotor3002located inward from the stator200is also rotatable under the rotating magnetic field of the stator200.

Power Tool Set

FIG.32is a schematic diagram of an electric work machine set1000according to the present embodiment. The electric work machine set1000includes an electric work machine1and an electric work machine101. The electric work machine1is an impact driver as an example of a power tool in the first embodiment described above. The electric work machine101is a chain saw as an example of outdoor power equipment in the second embodiment described above.

The electric work machine1includes a first motor6001. The first motor6001is the same as the motor601in the first embodiment described above. The first motor6001includes a stator200and a first rotor3001that can be combined with the stator200.

The electric work machine101includes a second motor6002. The second motor6002is the same as the motor602in the second embodiment described above. The second motor6002includes a stator200and a second rotor3002that can be combined with the stator200.

The number of poles in the first rotor3001is determined based on output conditions requested from a first output unit701in the first motor6001. The number of poles in the second rotor3002is determined based on output conditions requested from a second output unit702in the second motor6002. The first output unit701in the first motor6001includes a rotor shaft32in the first rotor3001. The second output unit702in the second motor6002includes a rotor shaft32in the second rotor3002.

The output conditions for the first output unit701include the rotational speed of the first output unit701. The output conditions for the second output unit702include the rotational speed of the second output unit702.

When the first output unit701in the first motor6001has a higher requested rotational speed than the second output unit702in the second motor6002, the first rotor3001has a smaller number of poles than the second rotor3002. When the first output unit701in the first motor6001has a lower requested rotational speed than the second output unit702in the second motor6002, the first rotor3001has a greater number of poles than the second rotor3002.

In the present embodiment, the first output unit701in the first motor6001has a higher requested rotational speed than the second output unit702in the second motor6002. The first rotor3001thus has a smaller number of poles than the second rotor3002. In other words, the first rotor3001has four poles, and the second rotor3002has eight poles as described above.

FIG.33is a graph showing the relationship between the number of poles in the rotor300in the present embodiment, the drive current supplied to the coils24, and the rotational speed of the output unit (the first output unit701or the second output unit702) in the rotor300.

InFIG.33, line Lc indicates the relationship between the drive current and the rotational speed for the first motor6001including the first rotor3001with four poles. Line Ld indicates the relationship between the drive current and the rotational speed for the second motor6002including the second rotor3002with eight poles. As shown inFIG.33, when a predetermined drive current is supplied to the coils24, the first output unit701in the first motor6001with four poles has a higher rotational speed than the second output unit702in the second motor6002with eight poles.

The output conditions for the first output unit701may include the torque of the first output unit701. The output conditions for the second output unit702may include the torque of the second output unit702.

When the first output unit701in the first motor6001has higher requested torque than the second output unit702in the second motor6002, the first rotor3001has a greater number of poles than the second rotor3002. When the first output unit701in the first motor6001has lower requested torque than the second output unit702in the second motor6002, the first rotor3001has a smaller number of poles than the second rotor3002.

In the present embodiment, the first output unit701in the first motor6001has lower requested torque than the second output unit702in the second motor6002. The first rotor3001thus has a smaller number of poles than the second rotor3002. In other words, the first rotor3001has four poles, and the second rotor3002has eight poles as described above.

The stator200may have any number of teeth21T (coils24) other than six teeth.

FIG.34is a table showing the relationship between the number of teeth21T on the stator200and the number of poles in the rotor300that can be combined with the stator200in the present embodiment. The teeth21T and the coils24are equal in number. As shown inFIG.34, the stator core21in the stator200satisfies the condition T=3×N, where T is the number of teeth21T and N is a natural number. The rotor300that can be combined with the stator200has an even number of poles.

For the stator core21in the stator200satisfying the condition T=3×N (where the natural number N is 1), or in other words, the number T of teeth21T on the stator200is 3(=3×N), the number of poles in the rotor300that can be combined with the stator200is 2(=2×N) and 4(=4×N). With the number T of teeth21T being 3, when the number of poles in the first rotor3001is set to one of 2 or 4, the number of poles in the second rotor3002is set to the other one of 2 or 4 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 2, and the number of poles in the second rotor3002is set to 4.

For the stator core21in the stator200satisfying the condition T=3×N (where the natural number N is 2), or in other words, the number T of teeth21T on the stator200is 6(=3×N), the number of poles in the rotor300that can be combined with the stator200is 4(=2×N) and8(=4×N). With the number T of teeth21T being 6, when the number of poles in the first rotor3001is set to one of 4 or 8, the number of poles in the second rotor3002is set to the other one of 4 or 8 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 4, and the number of poles in the second rotor3002is set to 8.

For the stator core21in the stator200satisfying the condition T=3×3×N (where the natural number N is 1), or in other words, the number T of teeth21T on the stator200is 9(=3×3×N), the number of poles in the rotor300that can be combined with the stator200is 6(=6×N), 8(=8×N), 10(=10×N), and 12(=12×N). With the number T of teeth21T being 9, when the number of poles in the first rotor3001is set to one of 6, 8, 10, or 12, the number of poles in the second rotor3002is set to another one of 6, 8, 10, or 12 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 6, and the number of poles in the second rotor3002is set to any one of 8, 10, or 12.

For the stator core21in the stator200satisfying the condition T=3×4×N (where the natural number N is 1), or in other words, the number T of teeth21T on the stator200is 12 (=3×4×N), the number of poles in the rotor300that can be combined with the stator200is 8 (8×N), 10(=10×N), 14(=14×N), and 16(=16×N). With the number T of teeth21T being 12, when the number of poles in the first rotor3001is set to one of 8, 10, 14, or 16, the number of poles in the second rotor3002is set to another one of 8, 10, 14, or 16 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 8, and the number of poles in the second rotor3002is set to any one of 10, 14, or 16.

For the stator core21in the stator200satisfying the condition T=3×5×N (where the natural number N is 1), or in other words, the number T of teeth21T on the stator200is 15 (=3×5×N), the number of poles in the rotor300that can be combined with the stator200is 10 (10×N), and 14(=14×N), 16(=16×N), and 20(=20×N). With the number T of teeth21T being 15, when the number of poles in the first rotor3001is set to one of 10, 14, 16, or 20, the number of poles in the second rotor3002is set to another one of 10, 14, 16, or 20 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 10, and the number of poles in the second rotor3002is set to any one of 14, 16, or 20.

For the stator core21in the stator200satisfying the condition T=3×3×N (where the natural number N is 2), or in other words, the number T of teeth21T on the stator200is 18 (=3×3×N), the number of poles in the rotor300that can be combined with the stator200is 12 (=6×N), 16(=8×N), 20(=10×N), and 24(=12×N). With the number T of teeth21T being 18, when the number of poles in the first rotor3001is set to one of 12, 16, 20, or 24, the number of poles in the second rotor3002is set to another one of 12, 16, 20, or 24 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 12, and the number of poles in the second rotor3002is set to any one of 16, 20, or 24.

For the stator core21in the stator200satisfying the condition T=3×N (where the natural number N is 7), or in other words, the number T of teeth21T on the stator200is 21(=3×N), the number of poles in the rotor300that can be combined with the stator200is 14(=2×N) and 28(=4×N). With the number T of teeth21T being 21, when the number of poles in the first rotor3001is set to one of 14 or 28, the number of poles in the second rotor3002is set to the other one of 14 or 28 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 14, and the number of poles in the second rotor3002is set to 28.

For the stator core21in the stator200satisfying the condition T=3×4×N (where the natural number N is 2), or in other words, the number T of teeth21T on the stator200is 24 (=3×4×N), the number of poles in the rotor300that can be combined with the stator200is 16 (8×N),20(=10×N),28(=14×N), and 32(=16×N). With the number T of teeth21T being 24, when the number of poles in the first rotor3001is set to one of 16, 20, 28, or 32, the number of poles in the second rotor3002is set to another one of 16, 20, 28, or 32 different from the number of poles in the first rotor3001. When the first output unit701has a higher requested rotational speed than the second output unit702, for example, the number of poles in the first rotor3001is set to 16, and the number of poles in the second rotor3002is set to any one of 20, 28, or 32.

As described above, one of multiple types of rotors300can be combined with one type of stator20in the present embodiment. This reduces the production cost of the first motor6001and the second motor6002. For example, the production facility for the first motor6001can be used to produce the second motor6002. The reduced production cost of the first motor6001and the second motor6002reduces the production cost of the electric work machine1and the electric work machine101. In addition, the first motor6001and the second motor6002can achieve the requested output characteristics simply by combining the stator20with different types of rotors300, without different motors being produced for each type of electric work machine.

The first rotor3001and the second rotor3002are equal in outer diameter. This allows the first rotor3001or the second rotor3002located inward from the stator20to rotate smoothly.

The number of poles in the first rotor3001is determined based on the output conditions requested from the first output unit701in the first motor6001. Of multiple types of rotors300with different numbers of poles, any type of rotor300may be combined as the first rotor3001with the single type of stator20, thus allowing the first output unit701to output power satisfying the requested output conditions.

Other Embodiments

FIG.35is a schematic diagram describing the relationship between a stator200and a rotor300in another example of the present embodiment. In the embodiment described above, one type of stator200can be combined with different types of rotors300. Different types of stators200may be combined with different types of rotors300.

As shown inFIG.35, the stator200includes a first stator201and a second stator202. The first motor6001in the electric work machine1includes the first stator201and a first rotor3001that can be combined with the first stator201. The first stator201includes a first stator core211and multiple first coils241each wound around the corresponding teeth21T on the first stator core211. The controller9in the electric work machine1supplies a drive current to the first coils241in the first stator201to magnetize the teeth21T on the first stator core211. This rotates the first rotor3001about the rotation axis AX.

The first stator201partially has the same structure as the second stator202. The first stator201partially has a different structure from the second stator202.

The first stator core211and a second stator core212in the second stator202, which is used in the second motor6002in another electric work machine101, are equal in shape in a plane orthogonal to the rotation axis AX. The first rotor3001can be combined with the second stator202.

The first stator core211has a length (corresponding to an axial dimension) different from the length of the second stator core212.

The first stator core211has a length determined based on output conditions requested from a first output unit701in the first motor6001. The second stator core212has a length determined based on output conditions requested from a second output unit702in the second motor6002.

The output conditions for the first output unit701include the rotational speed of the first output unit701. The output conditions for the second output unit702include the rotational speed of the second output unit702.

When the first output unit701in the first motor6001has a higher requested rotational speed than the second output unit702in the second motor6002, the first stator core211is shorter than the second stator core212. When the first output unit701in the first motor6001has a lower requested rotational speed than the second output unit702in the second motor6002, the first stator core211is longer than the second stator core212.

In the present embodiment, the first output unit701in the first motor6001has a higher requested rotational speed than the second output unit702in the second motor6002. The first stator core211is thus shorter than the second stator core212.

The output conditions for the first output unit701may include the torque of the first output unit701. The output conditions for the second output unit702may include the torque of the second output unit702.

When the first output unit701in the first motor6001has higher requested torque than the second output unit702in the second motor6002, the first stator core211is longer than the second stator core212. When the first output unit701in the first motor6001has lower requested torque than the second output unit702in the second motor6002, the first stator core211is shorter than the second stator core212.

In the present embodiment, the first output unit701in the first motor6001has lower requested torque than the second output unit702in the second motor6002. The first stator core211is thus shorter than the second stator core212.

The second stator202includes the second stator core212and multiple second coils242each wound around the corresponding teeth21T on the second stator core212. The teeth21T on the first stator201and the teeth21T on the second stator202are equal in number. The first coils241in the first stator201(six in the present embodiment) and the second coils242in the second stator202(six in the present embodiment) are equal in number.

The first coils241are connected in the same manner as the second coils242. When the first coils241are delta-connected as described with reference toFIG.7, the second coils242are also delta-connected.

The first coil241and the second coil242are equal in wire diameter. The wire diameter of the first coil241refers to the thickness (diameter) of a wire included in the first coil241. The wire diameter of the second coil242refers to the thickness (diameter) of a wire included in the second coil242.

The first coil241and the second coil242each have an equal number of turns. The number of turns of the first coil241refers to the number of times the wire included in the first coil241is wound around the corresponding tooth21T on the first stator core211. The number of turns of the second coil242refers to the number of times the wire included in the second coil242is wound around the corresponding to tooth21T on the second stator core212.

FIG.36is a flowchart of a manufacturing method for an electric work machine set1000in the other example of the present embodiment. InFIG.36, a first electric work machine refers to the electric work machine1described above. A second electric work machine refers to the electric work machine101described above.

The first motor6001is produced for the first electric work machine. To produce the first motor6001, the first stator core211is produced. Multiple first steel plates are stacked on one another to produce the first stator core211(step SA1).

Multiple first coils241each are then wound around the corresponding tooth21T on the first stator core211. The first coils241are wound around the teeth21T in a first connection manner (step SA2).

The first coils241are wound around the corresponding teeth21T on the first stator core211to produce the first stator201. The resultant first stator201is then combined with the first rotor3001having a first number of poles. This completes the first motor6001(step SA3). The first motor6001is used to manufacture the first electric work machine.

The second motor6002is produced for the second electric work machine. To produce the second motor6002, the second stator core212is produced. Multiple second steel plates are stacked on one another to produce the second stator core212(step SB1).

The second steel plate for the second stator core212has the same shape and the same dimensions as the first steel plate for the first stator core211. This allows the first stator core211and the second stator core212to be equal in shape and in dimension in a plane orthogonal to the rotation axis AX. The first stator core211has a length adjustable by controlling the number of first steel plates to be stacked. The second stator core212has a length adjustable by controlling the number of second steel plates to be stacked.

Multiple second coils242each are then wound around the corresponding tooth21T on the second stator core212. The second coils242are wound around the teeth21T in a second connection manner (step SB2).

The second connection manner for the second coils242is the same as the first connection manner for the first coils241.

The second coils242are wound around the corresponding teeth21T on the second stator core212to produce the second stator202. The resultant second stator202is then combined with the second rotor3002having a second number of poles. This completes the second motor6002(step SB3).

The second number of poles in the second rotor3002is different from the first number of poles in the first rotor3001.

The second motor6002is used to manufacture the second electric work machine.

The second rotor3002can be combined with the first stator201. The second rotor3002is rotatable relative to the second stator202and rotatable relative to the first stator201. The first stator201and the second rotor3002may be combined to produce a third motor. Similarly, the first rotor3001can be combined with the second stator202. The first rotor3001is rotatable relative to the first stator201and rotatable relative to the second stator202. The second stator202and the first rotor3001may be combined to produce a fourth motor (step SC).

The third motor may be used in one or both of the first electric work machine and the second electric work machine. The fourth motor may be used in one or both of the first electric work machine and the second electric work machine. The third motor may be used in a third electric work machine different from the first electric work machine and the second electric work machine. The fourth motor may be used in a fourth electric work machine different from the first electric work machine and the second electric work machine.

As described above, although the first stator201has a structure partially different from the structure of the second stator202, the first rotor3001that can be combined with the first stator201can also be combined with the second stator202, thus reducing the production cost of the first motor6001and the second motor6002. The first stator core211and the second stator core212in the second stator202are equal in shape in a plane orthogonal to the rotation axis AX. The first rotor3001that can be combined with the first stator201can thus also be combined with the second stator202.

As described with reference toFIGS.31and32and other figures, the first stator core211is the same as the second stator core212. In other words, one type of stator core21can be combined with the first rotor3001or the second rotor3002, reducing the production cost of the first motor6001and the second motor6002more effectively.

In the present embodiment, the first rotor3001and the second rotor3002may be equal in length (corresponding to an axial dimension).

In the present embodiment, the first rotor3001and the second rotor3002may not be equal in outer diameter.

In the present embodiment, the first coil241and the second coil242may have different wire diameters. The first coil241and the second coil242may have different numbers of turns.

In the present embodiment, the first coils241are delta-connected, the second coils242are delta-connected, and these delta-connections are parallel to each other as described with reference toFIG.7. The first coil241may be connected in the same manner as the second coil242, and are not limited to the connection manner described with reference toFIG.7.

FIGS.37to39are schematic diagrams of connected coils24(241 and 242) in other examples of the present embodiment. As shown inFIG.37, the coils24(241 and 242) may be delta-connected in series. As shown inFIG.38, the coils24(241 and 242) may be Y-connected in parallel. As shown inFIG.39, the coils24(241 and 242) may be Y-connected in series.

The motor in the present embodiment is an IPM motor. The motor may be a surface permanent magnetic (SPM) motor with permanent magnets attached to the outer surface of the rotor core. In some embodiments, the first rotor3001may be an IPM motor and the second rotor3002may be an SPM motor.

The motor in the present embodiment is a brushless inner-rotor motor. The motor may be a brushless outer-rotor motor.

Other Embodiments

In the above embodiments, the first portion61of the first core311has the dimension W1smaller than the dimension W2of the second portion62of the second core312. The first core311thus generates smaller reluctance torque than the second core312relative to the stator20. The adjustment of the reluctance torque of the first core311and the second core312is not limited to the adjustment of the dimensions W1and W2.

FIG.40is a partially enlarged cross-sectional view of a first core311in another embodiment.FIG.41is a partially enlarged cross-sectional view of a second core312in the other embodiment. As in the embodiments described above, the first core311and the second core312are adjacent to each other in the axial direction. As shown inFIG.40, the first core311has multiple first slots51located at intervals in the circumferential direction. As shown inFIG.41, the second core312has multiple second slots52located at intervals in the circumferential direction. The permanent magnets33are received in the respective first slots51and the respective second slots52. First portions61of the first core311each are located between first slots51adjacent in the circumferential direction. Second portions62of the second core312each are located between the second slots52adjacent in the circumferential direction. In the circumferential direction, the first portion61has the dimension W1equal to the dimension W2of the second portion62. As shown inFIG.40, holes63are located in the first portions61. As shown inFIG.41, no holes are located in the second portions62. The holes63in the first portions61cause the first core311to generate smaller reluctance torque than the second core312relative to the stator20.

The electric work machine1according to the above embodiments is an impact driver as an example of a power tool. The power tool is not limited to an impact driver. Examples of the power tool include a driver drill, a vibration driver drill, an angle drill, a screwdriver, a hammer, a hammer drill, a circular saw, and a reciprocating saw.

The electric work machine101according to the above embodiments is a chain saw as an example of outdoor power equipment. The outdoor power equipment is not limited to a chain saw. Examples of the outdoor power equipment include a hedge trimmer, a lawn mower, a mowing machine, and a blower.

In the above embodiments, the electric work machine may be a cleaner.

In the above embodiments, the electric work machine is powered by the battery pack14attached to the battery mount. In some embodiments, the electric work machine may use utility power (alternating current power supply).

REFERENCE SIGNS LIST

1electric work machine (impact driver)2housing2A motor compartment2B grip2C controller compartment3rear case4hammer case5battery mount7fan8anvil8A insertion hole9controller10trigger switch11forward-reverse switch lever12operation panel13lamp14battery pack15inlet16outlet17chuck unit18screw19through-hole20stator21stator core21T tooth22front insulator22D threaded hole22P protrusion22S support22T protrusion23rear insulator23T protrusion24coil24UU-phase coil24U1U-phase coil24U2U-phase coil24VV-phase coil24V1V-phase coil24V2V-phase coil24W W-phase coil24W1W-phase coil24W2W-phase coil25power line25UU-phase power line25VV-phase power line25W W-phase power line26fusing terminal26UU-phase fusing terminal26VV-phase fusing terminal26W W-phase fusing terminal27short-circuiting member27A opening27UU-phase short-circuiting member27VV-phase short-circuiting member27W W-phase short-circuiting member28insulating member28A body28B screw boss28C support28D opening29connection wire29E winding end29S winding start31rotor core31F front end (first end)31R rear end (second end)32rotor shaft33permanent magnet33A inner surface33B outer surface33C front surface33D rear surface33E first side surface33F second side surface35first steel plate36second steel plate37opening38opening39A recess39B recess40sensor board41plate42screw boss43magnetic sensor44signal line45opening50magnet slot51first slot51A first support surface51B second support surface51E third support surface51F fourth support surface51G first extension surface51H first facing surface51I first connecting surface51J second extension surface51K second facing surface51L second connecting surface52second slot52A fifth support surface52B sixth support surface52E seventh support surface52F eighth support surface52G third facing surface52H third extension surface52I third connecting surface52J fourth facing surface52K fourth extension surface52L fourth connecting surface61first portion62second portion63hole71first space72second space73first resin portion74second resin portion101electric work machine102housing103hand guard104first grip105battery mount106trigger switch107trigger lock lever108guide bar109saw chain110motor compartment111battery holder112second grip200stator201first stator202second stator211first stator core212second stator core241first coil242second coil300rotor301rotor301B rotor302rotor311first core311F front surface311R rear surface311S outer surface311T inner surface312second core312F front surface312R rear surface312S outer surface312T inner surface313third core331first permanent magnet332second permanent magnet601motor602motor701first output unit702second output unit1000electric work machine set3001first rotor3002second rotor6001first motor6002second motorC1distanceC2distanceE1dimensionE2dimensionH1dimensionH2dimensionL1dimensionL2dimensionLa lineLb lineLc lineLd lineR1distanceR2distanceT1thicknessT2thicknessVn arrowVs arrowW1dimensionW2dimension