Patent Application
20220247268
This application claims the priority benefit of Japan Application No. 2021-012789, filed on Jan. 29, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The disclosure relates to a permanent magnet-embedded motor including a stator in which a coil is wound and a rotor in which a permanent magnet is embedded, and a pump device using the same as a drive source.
As a conventional permanent magnet-embedded motor, a permanent magnet-type motor including an annular stator having teeth and slots disposed in a circumferential direction, coils wound around the teeth, and a rotor that is rotatably disposed inside the stator and in which a skew is given to embedding holes disposed in the circumferential direction to embed permanent magnets therein, in which the permanent magnets are embedded in multiple stages and an angle difference is provided for the permanent magnets in each stage to secure a skew with respect to the embedding holes of the rotor is known (for example, Patent Document 1).
In this permanent magnet-type motor, a cogging torque acting as a disturbance can be reduced by securing a skew in the permanent magnet, but since a plurality of permanent magnets is disposed in multiple stages in an axial direction of the rotating shaft, the structure is complicated, and this causes an increase in number of parts and an increase in costs.
Also, another permanent magnet-embedded motor including an annular stator having teeth and slots disposed in a circumferential direction, coils wound around the teeth, and a rotor that is rotatably disposed inside the stator and has main permanent magnets embedded in embedding holes disposed in the circumferential direction, in which a plurality of auxiliary permanent magnets is embedded in the rotor in addition to the main permanent magnets to collect a magnetic flux closer to the center of the main permanent magnets (at the center of the magnetic pole piece of the rotor) is known (for example, Patent Document 2).
In this permanent magnet-embedded motor, a cogging torque can be reduced by embedding the plurality of auxiliary permanent magnets in the rotor, but since the plurality of auxiliary permanent magnets is required in addition to the main permanent magnets, the structure is complicated, and this causes an increase in number of parts and an increase in costs.
The disclosure has been made in view of the above-described circumstances and provides a permanent magnet-embedded motor capable of reducing a cogging torque while simplifying the structure and reducing costs in view of the above-described problems of the conventional technologies, and a pump device using the same as a drive source.
A permanent magnet-embedded motor of the disclosure has a configuration including: a stator, including: a stator core in an annular shape having teeth and slots disposed in a circumferential direction, and coils wound around the teeth; and a rotor, including: a rotor core having insertion fitting holes disposed to face the teeth of the stator and disposed in the circumferential direction, and permanent magnets inserted and fitted into the insertion fitting holes, in which the rotor core includes: a groove-shaped recessed part, provided between the insertion fitting holes in the circumferential direction to define an outer circumferential magnetic pole part which generates a magnetic pole corresponding to each of the permanent magnets; a pair of notch parts, provided from both ends toward a center side of each of the outer circumferential magnetic pole parts in the circumferential direction to be recessed inward with respect to an outer circumferential contour; and an outer circumferential magnetic pole surface, sandwiched between the pair of notch parts.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which the insertion fitting hole has a cross-sectional shape which is long in a perpendicular direction perpendicular to a radial direction of the rotor, and the permanent magnet has a flat plate shape having a rectangular cross section which is long in the perpendicular direction and is inserted and fitted into the insertion fitting hole with gaps provided at both ends in the perpendicular direction.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which the groove-shaped recessed part is provided to have a space having a semicircular cross section, the insertion fitting hole has a cross-sectional shape which is long in a perpendicular direction with respect to a radial direction of the rotor and includes a convexly curved surface protruding inward following a wall part of the groove-shaped recessed part at both ends in the perpendicular direction, and the permanent magnet has a flat plate shape having a rectangular cross section which is long in the perpendicular direction and is inserted and fitted into the insertion fitting hole with gaps provided at both ends in the perpendicular direction.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which when a width dimension of the outer circumferential magnetic pole surface is Pw, and a width dimension of the permanent magnet in the perpendicular direction is Mw, Pw<Mw is satisfied.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which when a width dimension of the outer circumferential magnetic pole surface is Pw, and a width dimension of the permanent magnet in the perpendicular direction is Mw, a value of (Mw−Pw)/2=Δw is set to 3 mm or less.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which the pair of notch parts each include: a flat surface, extending parallel to a perpendicular direction perpendicular to a radial direction of the rotor and parallel to a rotation center line of the rotor; and a rising surface, rising from the flat surface toward the outer circumferential magnetic pole surface.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which a wall thickness dimension of a wall part defining the flat surface is provided to be substantially the same as a wall thickness dimension of a wall part defining the groove-shaped recessed part.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which when a distal end width dimension of the teeth is Tw, an opening width dimension of the slot is Sw, and a width dimension of the outer circumferential magnetic pole surface is Pw, a relationship of Tw:Sw:Pw=4.5 to 6.5:1 to 3:5 to 7 is satisfied.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which the rotor core includes a filling hole provided to be communicating with the insertion fitting hole and filled with an adhesive on an inner side of the insertion fitting hole in a radial direction.
In the permanent magnet-embedded motor described above, a configuration may be employed, in which a number of magnetic poles of the rotor is 2n (n is a natural number), and a number of teeth and slots of the stator is 3n (n is a natural number), respectively.
A pump device of the disclosure has a configuration including: a pump unit which performs suctioning and discharging of a fluid; a rotating shaft, connected to the pump unit; and a drive source, exerting a driving force on the rotating shaft, in which the drive source is any one of the permanent magnet-embedded motors having configurations described above.
In the pump unit described above, a configuration may be employed in which, the pump unit is a trochoid pump including: an inner rotor to which the rotating shaft is connected; and an outer rotor that meshes with the inner rotor.
According to the permanent magnet-embedded motor having the above-described configuration, the cogging torque can be reduced while simplifying the structure and reducing costs. Also, when such a permanent magnet-embedded motor is used as a drive source, a pump device with less vibration and noise can be obtained.
Hereinafter, embodiments of the disclosure will be described with reference to the accompanying drawings.
As illustrated in
The pump unit U suctions and discharges a fluid (here, oil), and is a trochoid pump including an inner rotor 11 and an outer rotor 12.
As illustrated in
The housing main body 1 is formed of an aluminum material or the like, and as illustrated in
The communication passage 1c is formed in a cylindrical shape with a rotation center line L of the permanent magnet-embedded motor M as a center, and through which the rotating shaft 5 is inserted with a predetermined gap therebetween.
The annular recessed part 1d is formed in an annular shape with the rotation center line L as a center so that a lip-type seal Ls is fitted therein.
The annular recessed part 1e is formed in an annular shape with the rotation center line L as a center so that a bearing B1 rotatably supporting the rotating shaft 5 is fitted therein by interposing a washer W between itself and the lip-type seal Ls.
The pump cover 2 is formed of an aluminum material or the like, is joined to the end surface 1f of the housing main body 1 to cover the housing recessed part 1a, and includes a suction port 2a for suctioning a fluid and a discharge port 2b for discharging a pressurized fluid as illustrated in
Then, the pump cover 2 is joined to the end surface 1f of the housing main body 1 in a state in which the pump unit U is housed in the housing recessed part 1a, and then is fastened and fixed by a screw b1.
The motor cover 3 is formed of a resin material, is joined to the end surface 1g of the housing main body 1 to cover the housing recessed part 1b, and as illustrated in
The through hole 3a is formed so that a detected unit 5b fixed to an end portion of the rotating shaft 5 is inserted.
The annular recessed part 3b is formed in an annular shape with the rotation center line L as a center so that a cylindrical metal holder 3e is fitted and fixed. The metal holder 3e fits and holds a bearing B2 that rotatably supports the rotating shaft 5.
Then, the motor cover 3 is joined to the end surface 1g of the housing main body 1, has the substrate cover 4 joined thereto from the outside, and is fixed between the two by being fastened with screws b2.
The substrate cover 4 is formed of a metal plate, a resin material, or the like, and is fastened and fixed to the end surface 1g of the housing main body 1 with the screws b2 in a state in which the motor cover 3 is sandwiched therebetween to cover the circuit board CB.
The rotating shaft 5 is formed in a columnar shape centered on the rotation center line L using a metal material, and as illustrated in
Then, the rotating shaft 5 is fitted into a shaft hole 55 of the rotor core 50 included in the permanent magnet-embedded motor M and connected to the inner rotor 11 of the pump unit U by the connecting part 5a, is sealed by the lip-type seal Ls on the outer circumference, is rotatably supported by the bearings B1 and B2, and thereby transmits a rotational force of the rotor Rt to the inner rotor 11.
The detected unit 5b is formed by fitting permanent magnets into the annular holder so that six N poles and S poles alternate around the rotation center line L and is disposed to face a detection sensor C1 mounted on the circuit board CB as illustrated in
Then, the detected unit 5b functions as a detection target of the detection sensor C1 that detects a rotational angular position of the rotating shaft 5, that is, the rotor Rt.
As illustrated in
The inner rotor 11 is formed using a material such as steel or sintered steel in a substantially star shape that defines an end surface sliding between a bottom wall surface of the housing recessed part 1a of the housing main body 1 and an inner wall surface of the pump cover 2. The inner rotor 11 is formed as an external gear with a trochoidal curved tooth profile including a fitting hole 11a, five protruding parts (peaks) and five recessed parts (valleys).
The fitting hole 11a is formed so that the connecting part 5a of the rotating shaft 5 is fitted thereto.
Then, the inner rotor 11 is rotated by the rotating shaft 5 in a direction of an arrow A in
The outer rotor 12 is formed using a material such as steel or sintered steel in an annular shape that defines the end surface sliding between the bottom wall surface of the housing recessed part 1a of the housing main body 1 and the inner wall surface of the pump cover 2. The outer rotor 12 is formed as an internal gear including a circular outer circumferential surface 12a, six protruding parts, and six recessed parts, and having a tooth profile that can mesh with the inner rotor 11.
The outer circumferential surface 12a comes into contact with an inner circumferential surface of the housing recessed part 1a to be rotatably supported around an axis displaced from the rotation center line L.
Then, the outer rotor 12 rotates at a speed lower than that of the inner rotor 11 while being interlocked with rotation of the inner rotor 11 that rotates around the rotation center line L.
Due to the inner rotor 11 and the outer rotor 12, a fluid is suctioned from the suction port 2a into a pump chamber and is discharged from the discharge port 2b while being pressurized.
The circuit board CB includes parts controlling driving of the permanent magnet-embedded motor M, on which wiring is printed and various electronic parts constituting a control circuit are mounted, and on which the detection sensor C1 facing the detected unit 5b is mounted as illustrated in
The detection sensor C1 is formed by three Hall elements disposed in an arc shape around the rotation center line L. Further, the detection sensor C1 is configured to detect a magnetic pole position (rotational angular position) in a rotation direction of the rotating shaft 5, that is, the rotor Rt.
As illustrated in
The stator core 20 is formed as a laminate that is press-formed using a steel plate made of a magnetic material and then laminated, and as illustrated in
The nine teeth 22 are formed to have the same shape as each other and are rotationally symmetrical with respect to the rotation center line L, and each have a distal end surface 22a that defines an arcuate surface.
The nine distal end surfaces 22a are disposed on a cylindrical surface having a predetermined diameter dimension and are disposed to face an outer circumferential contour 50a (outer circumferential magnetic pole surface 53b) of the rotor core 50 with a predetermined gap therebetween.
The nine slots 23 are formed to have the same shape as each other and are rotationally symmetrical with respect to the rotation center line L, and each have an opening 23a having an opening width dimension Sw between the teeth 22 on both sides as illustrated in
The bobbin 30 is formed in a two-part structure using a resin material having electrical insulating properties and is incorporated so as to sandwich the stator core 20 in a direction of the rotation center line L.
The coil 40 employs a concentrated winding structure wound around each of the nine teeth 22 with the bobbin 30 interposed therebetween, and these are divided into three phases and electrically connected.
The rotor core 50 is formed as a laminate that is press-formed using a steel plate made of a magnetic material and then laminated and is formed to define the cylindrical outer circumferential contour 50a facing the teeth 22 (distal end surface 22a) of the stator core 20 with a predetermined gap therebetween as illustrated in
As illustrated in
Here, the six insertion fitting holes 51, the six groove-shaped recessed parts 52, the six outer circumferential magnetic pole parts 53, the six filling holes 54, and the six long holes 56 are each formed to be rotationally symmetrical with respect to the rotation center line L and are each formed to be line-symmetrical with respect to a straight line DL in a radial direction except for the long holes 56, and therefore each one of them will be described below.
The insertion fitting hole 51 is a region to which the permanent magnet 60 is inserted and fixed, that is, an embedded region of the permanent magnet 60, and is formed to have a cross-sectional shape that is long in a perpendicular direction Pd perpendicular to the straight line DL of the rotor Rt in the radial direction as illustrated in
Specifically, the insertion fitting hole 51 is formed to include two flat surfaces 51a and 51b parallel to the perpendicular direction Pd and two convexly curved surfaces 51c each protruding inward following a wall part 52a of the groove-shaped recessed part 52 at both ends in the perpendicular direction Pd.
When the insertion fitting hole 51 includes two convexly curved surfaces 51c, displacement of the permanent magnet 60 in the perpendicular direction Pd can be suppressed or prevented while providing gaps G on both sides when the permanent magnet 60 is inserted into the insertion fitting hole 51.
The groove-shaped recessed part 52 is formed to have a space having a semicircular cross section by the wall part 52a having a wall thickness dimension Tg between the insertion fitting holes 51 and 51 in the circumferential direction to define the outer circumferential magnetic pole part 53 by dividing the outer circumferential contour 50a in the circumferential direction.
The groove-shaped recessed part 52 functions as a flux barrier that suppresses or prevents leakage and short-circuiting of magnetic lines of force and also serves as a positioning part for inserting a jig for positioning the rotor core 50 when the permanent magnet 60 is assembled into the insertion fitting hole 51.
Here, since the wall thickness dimension Tg of the wall part 52a is formed to be relatively thin within an allowable range in terms of mechanical strength, short-circuiting of magnetic lines of force between adjacent permanent magnets 60 and 60 can be suppressed or prevented.
The outer circumferential magnetic pole part 53 is a region in which a magnetic pole corresponding to the permanent magnet 60 inserted and fitted in the insertion fitting hole 51 is generated, has a shape line-symmetrical with respect to the straight line DL in the radial direction, and includes a pair of notch parts 53a and 53a and an outer circumferential magnetic pole surface 53b as illustrated in
The pair of notch parts 53a and 53a are line-symmetrical with respect to the straight line DL and are formed from both ends toward a center (straight line DL) side of the outer circumferential magnetic pole part 53 in the circumferential direction to be recessed inward with respect to the outer circumferential contour 50a.
Specifically, as illustrated in
Here, a wall thickness dimension Tc of a wall part 53a12 defining the flat surface 53a1 is formed to be substantially the same as the wall thickness dimension Tg of the wall part 52a defining the groove-shaped recessed part 52.
Then, the pair of notch parts 53a and 53a function as a flux barrier that increases a gap between the rotor core 50 and the teeth 22 (distal end surface 22a) of the stator core 20 and play a role of collecting magnetic lines of force flowing through the outer circumferential magnetic pole part 53 on the outer circumferential magnetic pole surface 53b close to the center to increase a useful magnetic flux toward the teeth 22.
The outer circumferential magnetic pole surface 53b is a region sandwiched by the pair of notch parts 53a and 53a in the circumferential direction, forms a curved surface having a curvature of 2/D when an outer diameter dimension of a cylindrical curved surface defining the outer circumferential contour 50a, that is, the outer circumferential contour 50a is assumed to be D, and faces the distal end surface 22a of the teeth 22 with a predetermined gap therebetween.
The filling hole 54 is a region filled with an adhesive for fixing the permanent magnet 60 and is formed in communication with the insertion fitting hole 51 on an inner side of the insertion fitting hole 51 in the radial direction.
That is, when the filling hole 54 is filled with an adhesive after the permanent magnet 60 is inserted into the insertion fitting hole 51, a surface of the permanent magnet 60 facing inward in the radial direction and the flat surface 51b of the insertion fitting hole 51 are adhered to each other.
As illustrated in
The long hole 56 is formed on a radial outer side of the shaft hole 55 to extend in a direction inclined with respect to the straight line DL. The long hole 56 allows elastic deformation of a peripheral region of the protrusion 55a when the rotating shaft 5 is fitted into the shaft hole 55. Thereby, a fitting operation of the rotating shaft 5 can be smoothly performed.
As illustrated in
Here, since the gaps G are provided on both sides of the permanent magnet 60, magnetic lines of force being self-short-circuited from the N pole to the S pole of the permanent magnet 60 can be prevented.
Also, since one permanent magnet 60 having a simple form of a flat plate shape is disposed corresponding to one outer circumferential magnetic pole part 53, a structure thereof can be simplified and costs can be reduced compared to a configuration in which a permanent magnet having a curved shape is disposed corresponding to one outer circumferential magnetic pole part 53 or a configuration in which a plurality of permanent magnets is disposed corresponding to one outer circumferential magnetic pole part 53.
In the permanent magnet-embedded motor M having the above-described configuration, as illustrated in
When the relationship is set in this way, magnetic lines of force emitted from the permanent magnet 60 can be collected on the center (straight line DL) side of the outer circumferential magnetic pole surface 53b while suppressing leakage from both sides of the outer circumferential magnetic pole part 53.
Particularly, a value of (Mw−Pw)/2=Δw is preferably set to 3 mm or less. Thereby, a useful magnetic flux contributing to a rotational torque can be increased while reducing a cogging torque.
Also, in the permanent magnet-embedded motor M having the above-described configuration, a relationship between the width dimension Pw of the outer circumferential magnetic pole surface 53b, the wall thickness dimension Tc of the wall part 53a12 defining the notch part 53a, and the cogging torque will be described with reference to
As is apparent from the results illustrated in
That is, when the wall thickness dimension Tc of the wall part 53a12 defining the flat surface 53a1 is To, the cogging torque is the smallest when the width dimension Pw of the outer circumferential magnetic pole surface 53b is in the vicinity of the value of Po, and the cogging torque shows V-shaped characteristic in which the cogging torque increases at specifications in which the width dimension Pw is smaller and larger than Po.
Therefore, in order to effectively reduce the cogging torque, as illustrated in
Also, since the cogging torque can be reduced as the value of the wall thickness dimension Tc becomes smaller as illustrated in
Here, when the wall thickness dimension Tg of the wall part 52a of the groove-shaped recessed part 52 is set to a value in a range of Tg−Δt to Tg+Δt, for example, when a tolerance thereof is ±Δt due to restrictions on mechanical strength, the value of the wall thickness dimension Tc is preferably set to a value in a range of To−Δt to To+Δt with the value of To as a median value as illustrated in
That is, the wall thickness dimension Tc of the wall part 53a12 defining the flat surface 53a1 is preferably set to be equivalent to the wall thickness dimension Tg of the wall part 52a defining the groove-shaped recessed part 52.
Results of simulating a distribution state of magnetic lines of force due to the permanent magnet 60 in the permanent magnet-embedded motor M having the above-described configuration will be described with reference to
In the comparative example, as illustrated in
Therefore, as illustrated in
As a result, a cogging torque trying to rotate the rotor Rt clockwise in an attempt to return to a magnetically stable state is generated. Also, in the comparative example, as illustrated in
On the other hand, in the example, as illustrated in
Therefore, as illustrated in
As a result, the cogging torque trying to rotate the rotor Rt clockwise in an attempt to return to a magnetically stable state is smaller than that in the comparative example.
Also, in the example, as illustrated in
The cogging torque of the example and the comparative example having the above-described configurations have results as illustrated in
As is apparent from the results shown in
Therefore, based on the above-described results, according to the results of the simulation by changing mutual dimensions of the distal end width dimension Tw of the teeth 22, the opening width dimension Sw of the slot 23, and the width dimension Pw of the outer circumferential magnetic pole surface 53b in the permanent magnet-embedded motor M, in a case of a relative shape relationship satisfying the relationship of Tw:Sw:Pw=4.5 to 6.5:1 to 3:5 to 7, it was ascertained that leakage of the magnetic flux from both end sides of the outer circumferential magnetic pole parts 53 could be suppressed to increase the useful magnetic flux toward the teeth 22, and the cogging torque could be effectively reduced.
As described above, according to the permanent magnet-embedded motor M having the above-described configuration, the cogging torque can be reduced while simplifying the structure and reducing costs.
Also, when the permanent magnet-embedded motor M having the above-described configuration is applied as a drive source of a pump device, a pump device with less vibration and noise can be obtained. Further, when such a pump device is applied for supply and circulation of an oil in an automobile or the like, vibration and noise in the automobile can be reduced.
Further, an operation of the permanent magnet-embedded motor M having the above-described configuration is the same as that of the conventional permanent magnet-embedded motor, and thus description thereof is omitted here.
In this embodiment, the rotor core 50 includes six insertion fitting holes 51, six groove-shaped recessed parts 52, six outer circumferential magnetic pole parts 53, six filling holes 54, a shaft hole 55, and six long holes 56.
The outer circumferential magnetic pole parts 53 each includes a pair of notch parts 153a and 153a and an outer circumferential magnetic pole surface 53b.
The pair of notch parts 153a and 153a are line-symmetrical with respect to a straight line DL and are formed from both ends toward a center (straight line DL) side of the outer circumferential magnetic pole part 53 in a circumferential direction to be recessed inward with respect to an outer circumferential contour 50a.
Specifically, the pair of notch parts 153a and 153a extend parallel to a rotation center line L and are formed as concave curved surfaces that are recessed inward with respect to the outer circumferential contour 50a and are connected to the outer circumferential magnetic pole surface 53b from both ends.
Also in this embodiment, since a wall thickness dimension of a wall part defining the pair of notch parts 153a and 153a is made small, similarly to that described above, a cogging torque can be reduced as compared with that in the comparative example in which the pair of notch parts 53a and 53a are not provided.
In the above-described embodiment, as a permanent magnet-embedded motor including a stator having a plurality of teeth and slots disposed in the circumferential direction, and a rotor having a plurality of insertion fitting holes disposed in the circumferential direction and a plurality of permanent magnets inserted and fitted in the insertion fitting holes, the permanent magnet-embedded motor M including the stator St having nine teeth 22 and slots 23 and the rotor Rt having six insertion fitting holes 51 (that is, six permanent magnets 60), that is the permanent magnet-embedded motor M in which the number of magnetic poles of the rotor Rt is six and the number of teeth and slots of the stator St is nine is illustrated.
However, the disclosure is not limited to the above-described configuration and can be similarly applied to a permanent magnet-embedded motor having another configuration that satisfies a condition in which the number of magnetic poles of the rotor is 2n (n is a natural number), and the number of teeth and slots of the stator is 3n (n is a natural number), respectively.
In the above-described embodiment, as the groove-shaped recessed part provided in the rotor core 50, the groove-shaped recessed part 52 forming a space having a semicircular cross section is illustrated, but the disclosure is not limited thereto, and a groove-shaped recessed part having another cross-sectional shape may be employed as long as it is formed between the insertion fitting holes in the circumferential direction to define the outer circumferential magnetic pole part that generates a magnetic pole corresponding to the permanent magnet.
In the above-described embodiment, as the insertion fitting hole provided in the rotor core 50, the insertion fitting hole 51 having the convexly curved surface 51c on both sides are illustrated, but the disclosure is not limited thereto, and an insertion fitting hole in which wall surfaces on both sides have another form may be employed.
In the above-described embodiment, in the pump device using the permanent magnet-embedded motor M as a drive source, a case in which a trochoid pump is employed as a pump unit is illustrated, but the disclosure is not limited thereto, and a vane pump or pumps of other types may be employed.
As described above, since the permanent magnet-embedded motor of the disclosure can be simplified in the structure, reduced in costs, and reduced in cogging torque, the permanent magnet-embedded motor is not only applicable as a drive source for pump devices but also useful as a drive source for various devices.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-012789 | Jan 2021 | JP | national |
