CN106208455B

CN106208455B - Rotor, motor, pump and cleaning device

Info

Publication number: CN106208455B
Application number: CN201510323877.9A
Authority: CN
Inventors: 李敏; 雷迪·马利克; 张小林
Original assignee: Johnson Electric Shenzhen Co Ltd
Current assignee: Johnson Electric Shenzhen Co Ltd
Priority date: 2014-12-11
Filing date: 2015-06-12
Publication date: 2024-03-05
Anticipated expiration: 2035-06-12
Also published as: CN106208455A; CN106208424A; CN204809997U; CN204810096U; ES2785377T3; CN106208582A; CN106194764A; CN106208582B; CN204810016U; CN106208581A; CN204810095U

Abstract

The invention discloses a rotor, a motor, a pump and a cleaning device. The rotor comprises a rotating shaft and two magnets fixed on the rotating shaft, wherein each magnet is provided with a radial outer surface, a radial inner surface and two connecting surfaces which are respectively connected with the radial outer surface and the radial inner surface at two sides, the radial outer surface comprises a cambered surface part, and the radial inner surfaces of the two magnets jointly form an inner hole for the rotating shaft to pass through. Wherein, the ratio of the polar arc angle of the magnet to 180 degrees is between 0.75 and 0.95.

Description

Rotor, motor, pump and cleaning device

Technical Field

The present invention relates to electric machines, and in particular to permanent magnet rotors for electric machines.

Background

The permanent magnet rotor generally comprises a rotating shaft and permanent magnets fixed on the rotating shaft, wherein the permanent magnets can be annular magnets, a plurality of magnetic poles are arranged along the circumferential direction, and the permanent magnets can also be a plurality of separated arc magnets. The cost of manufacturing the ring magnets is generally high, and for some applications, such as the drain pump of a dishwasher, very little vibration of the motor is generally required. The invention aims to provide a permanent magnet rotor with low cost and small vibration.

Disclosure of Invention

The invention provides a synchronous motor, which comprises a stator and a permanent magnet rotor capable of rotating relative to the stator, wherein the rotor comprises a rotating shaft and two magnets fixed on the rotating shaft, the magnets are provided with a radial outer surface, a radial inner surface and two connecting surfaces respectively connected with the radial outer surface and the radial inner surface at two sides, the radial outer surface comprises a cambered surface part, and the radial inner surfaces of the two magnets jointly form an inner hole for the rotating shaft to pass through; the stator comprises a stator magnetic core and a stator winding wound on the stator magnetic core, wherein the rotor runs at a constant speed at a rotating speed of 60f circles/min in a steady-state stage when the stator winding is connected with an alternating current power supply in series, wherein f is the frequency of the alternating current power supply; the stator magnetic core is provided with two opposite pole parts and a yoke part connected with the two pole parts, each pole part is provided with a pole arc surface opposite to the rotor, and an air gap is formed between the pole arc surface and the rotor; wherein, the ratio of the polar arc angle of the magnet to 180 degrees is between 0.75 and 0.95.

Preferably, the two pole portions have circumferential end portions disposed at a distance from each other, and a ratio between a distance between the circumferential end portions and a minimum width of the air gap is less than 2.

Preferably, the polar cambered surface is concentric with the rotor so as to form a main air gap with equal distance with the rotor; the arc surface is provided with a concave starting groove, and uneven air gaps with unequal intervals are formed between the starting groove and the rotor.

Preferably, the two magnets are fixed on the rotating shaft by an overmoulding piece, the outer surface of the overmoulding piece is concentric with the rotating shaft, the two connecting surfaces of the magnets are coplanar, and the ratio between the lengths of the two ends of the two connecting surfaces and the diameter of the outer surface of the overmoulding piece is between 0.82 and 0.95.

Preferably, the radial outer surface of the magnet further comprises a plane part extending from two circumferential ends of the cambered surface part to the connecting surface, the two plane parts of the radial outer surfaces of the two magnets on the same side are arranged in a coplanar manner, and the distance between the circumferential two ends of the two plane parts is between 2mm and 9.5 mm.

The invention also provides a rotor, which comprises a rotating shaft and two magnets fixed on the rotating shaft, wherein the magnets are provided with a radial outer surface, a radial inner surface and two connecting surfaces which are respectively connected with the radial outer surface and the radial inner surface at two sides, the radial outer surface comprises a cambered surface part, and the radial inner surfaces of the two magnets jointly form an inner hole for the rotating shaft to pass through; wherein, the ratio of the polar arc angle of the magnet to 180 degrees is between 0.75 and 0.95.

Preferably, the ratio of the polar arc angle of the magnet to 180 degrees is between 0.9 and 0.95.

Preferably, the two magnets are fixed on the rotating shaft by an over-molding member, the radial outer surfaces of the magnets further comprise planar portions extending from two circumferential ends of the cambered surface portion to the connecting surface, the radial outer surfaces of the two magnets are arranged in a coplanar manner on two planar portions on the same side, the over-molding member is provided with a positioning groove, and the positioning groove is arranged at the joint of the two magnets and completely covers the two planar portions in the circumferential direction.

In yet another aspect, the present invention provides a pump comprising: a pump housing having a pump chamber; an inlet and an outlet in communication with the pump chamber; an impeller disposed within the pump chamber; and a motor for driving the impeller, the motor comprising a stator and a rotor rotatable relative to the stator, the rotor having the characteristics of the rotor as described above.

In yet another aspect, the present invention provides a cleaning apparatus comprising: a washing chamber, a water supply passage supplying washing water to the washing chamber, a drain passage discharging the washing water to the outside, and a drain pump pumping the washing water in the washing chamber to the drain passage; wherein the drain pump has the features of the pump described above.

Compared with the traditional arc-shaped magnet, the rotor in the embodiment has larger pole arc angle of the magnet, can reduce the cogging torque of the motor, enables the rotor to rotate more smoothly, and has lower cost compared with the annular magnet.

Drawings

FIG. 1 illustrates a pump having an embodiment in accordance with the present invention;

FIG. 2 is an axial cross-sectional view of the pump of FIG. 1;

FIG. 3 is an axial cross-sectional view of the motor rotor of the pump of FIG. 1;

FIG. 4 shows a magnet of the rotor of FIG. 3;

FIG. 5 is a radial cross-sectional view of the motor rotor of the pump of FIG. 1 at the detent recess shown in FIG. 3;

FIG. 6 is a plan view of a motor removed portion of the pump of FIG. 1;

FIG. 7 is a plan view of a stator core of the motor of FIG. 6;

FIG. 8 illustrates another implementation of an insulated wire frame of a stator of the electric machine of FIG. 6;

FIG. 9 is a horizontally expanded schematic view of an insulated wire frame of a stator of the motor of FIG. 8;

FIG. 10 shows a pump housing cover of the pump of FIG. 1;

FIG. 11 is a view of the pump of FIG. 1 with the pump housing cover removed;

FIG. 12 shows a mounting block diagram of the motor rotor of the pump of FIG. 1;

FIG. 13 is a bottom view of the bottom plate of the pump of FIG. 1;

FIG. 14 shows an impeller of the pump of FIG. 1; and

fig. 15 shows a dishwasher having a pump according to a preferred embodiment of the present invention.

Detailed Description

The technical solution and other advantageous effects of the present invention will be made apparent by the following detailed description of the specific embodiments of the present invention with reference to the accompanying drawings. It is to be understood that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention. The dimensions shown in the drawings are for clarity of description only and are not limiting on the scale.

Referring to fig. 1 and 2, a pump 10 according to an embodiment of the present invention includes a pump housing 14 having a pump chamber 12, an inlet 16 and an outlet 18 in communication with the pump chamber 14, an impeller 20 rotatably disposed within the pump chamber 14, and a motor 22 for driving the impeller 20. The motor 22 is preferably a synchronous motor including a stator and a rotor 26 rotatable relative to the stator. The pump provided by the invention is especially suitable for the drainage pump of a washing device such as a dish washer, a washing machine and the like.

Referring to fig. 3 to 5, the rotor 26 includes a rotation shaft 28 and a magnet 30 fixed to the rotation shaft 28. In the preferred embodiment of the invention, the rotor 26 has two permanent magnets 30, the two magnets 30 forming two permanent magnetic poles of opposite polarity and being secured to the shaft 28 via an overmold 32. The overmold 32 comprises an inner ring 34, an outer ring 36, and two end plates 38 connecting the inner ring 34 and the outer ring 36 at both axial ends. An outer ring 36 is overmolded onto the magnet 30, the outer surface of which is concentric with the spindle 28. The inner ring 34 is overmolded onto the spindle 28. The two magnets 30 are fixed between the inner ring 34 and the outer ring 36 in the radial direction and between the two end plates 38 in the axial direction. The outer surface of the shaft 28 is provided with a concave-convex structure 39 to strengthen the bonding force between the over-molded member 32 and the shaft 28. Each magnet 30 circumferentially covers half a circumference and has a radially outer surface 40, a radially inner surface 42, and two connecting surfaces 44 connecting the radially outer surface 40 and the radially inner surface 42 on both sides, respectively. Preferably, the two connection surfaces 44 are planar and coplanar. The radially outer surface 40 includes a cambered surface portion 46 and a planar portion 48 extending from both circumferential ends of the cambered surface portion 46 to the connecting surface 44. The magnet 30 may be sintered from powder and the planar portion 48 may be used to position the molded magnet 30 for subsequent grinding and the like. The arcuate surface portion 46 of the outer surface 40 may be concentric with the radially inner surface 42. The radially inner surfaces 42 of the two magnets 30 together define an inner bore 50 for the shaft 28 to pass through. The inner ring 34 of the overmold 32 is molded between the radially inner surface 42 and the spindle 28.

Preferably, the ratio of the pole arc angle θ to 180 degrees of each magnet 30 is between 0.75 and 0.95, more preferably between 0.9 and 0.95. The polar arc angle referred to herein refers to the angle formed by the virtual line connecting the two circumferential ends of the arcuate surface portion 46 of the radially outer surface 40 of the magnet and the axis of the rotating shaft 28. The radially outer surfaces 40 of the two magnets 30 are arranged coplanar at two planar portions 48 on the same side, and the distance d1 between the circumferential ends of the two planar portions 48 is between 2mm and 9.5 mm. The ratio between the length d2 of the two co-planar connection surfaces 44 of the magnet 30 and the diameter d3 of the outer surface of the overmold 32 is between 0.82 and 0.95. In a preferred embodiment, the pole arc angle θ of the magnets 30 is greater than 166 degrees, and the distance d1 between the circumferential ends of the two coplanar planar segments 48 of the two magnets 30 is between 2mm and 2.5 mm. The axial end of the outer ring 36 of the overmold 32 has at least two circumferentially spaced locating grooves 52 for locating the two magnets 30 during the process of molding the overmold 32. Each positioning groove 52 is provided at the junction of the two magnets 30 and entirely covers the two planar portions 48 of the two magnets 30 on the same side in the circumferential direction.

Referring to fig. 6 and 7, the stator has a stator core 54 and a stator winding 56 wound around the stator core 54. In this embodiment, the stator core 54 has a bottom 58, two branches 60 extending from both ends of the bottom 58, and a pair of opposite pole portions 62 provided to the two branches 60, respectively. Preferably, the bottom 58 is in a strip shape, two branches 60 extend from two ends of the bottom 58 in parallel, and two pole portions 62 are opposite to each other and are disposed at ends of the two branches 60 away from the bottom 58. Each pole 62 has two sides 64 and 65 extending from the branch 60 substantially parallel to the base 58 and a pole arc 66 recessed between the sides 64 and 65, the outer surface of the rotor being opposite the pole arc 66 with an air gap therebetween.

Preferably, the base 58 and the two branches 60 are each independently formed. The base 58 may be assembled from a stack of sheet-like base members and the branches 60 may be assembled from a stack of sheet-like branch members. The base member and the branch members are each provided with an assembly hole 68 for fixing the stacked sheet members as one body. The end surfaces of the two branches 60 near one end of the bottom 58 are provided with protruding parts 70, and the two ends of the bottom are correspondingly provided with two recessed parts 72. After the base member and the branch members are assembled into an integral lamination structure, the protruding portions 70 of the two branches 60 are respectively and snap-connected with the two recessed portions 72 at the two ends of the base 58, so as to form a stator core whole. It will be appreciated that, as an alternative, the raised portion 70 may be provided at the bottom and the recessed portion 72 may be provided at the branches. In this embodiment, the maximum width b1 of the bottom 58 is not greater than the minimum distance b2 between the two branches 60 after splicing. The maximum length b3 of the base 58 is not greater than the maximum distance b4 between the base-facing side 64 of the branch 60 and the distal-most end of the branch 60 (the distal-most end of the boss 70 in this embodiment) near the end of the base. According to such an arrangement, the base 58 may be formed from material between the two branches 60, thereby saving material and reducing product costs. Further, the maximum length b3 of the bottom may be greater than the distance b5 between the bottom-facing side 64 of the branch 60 and the end of the branch 60 near the bottom end.

The two side circumferential ends of the two stator pole sections 62 have circumferential end sections 74 provided opposite to each other. The grooves 75 are arranged between the opposite circumferential end parts, so that the grooves 75 can form larger magnetic resistance and reduce magnetic leakage. A substantially uniform air gap is formed between the pole cambered surfaces 66 of the stator pole sections 62 and the outer surface of the rotor 26. The term substantially uniform air gap as used herein refers to a uniform air gap formed between a substantial portion of the stator and a substantial portion of the rotor, with a smaller portion being a non-uniform air gap. Preferably, the pole faces 66 of the stator poles are concentric with the rotor to form a primary air gap 76 of equal spacing, and the pole faces 66 are provided with recessed starter grooves 78 to form uneven air gaps of unequal spacing between the starter grooves 78 and the outer surface of the rotor 26. Preferably, the two start grooves 78 on the polar faces of the two polar portions 62 are diametrically symmetrical and extend from the circumferential end 74 of the polar portions. The above arrangement ensures that the rotor 26 has its pole axis S1 (shown in fig. 5) tilted at an angle relative to the central axis S2 of the stator pole sections 62 when at rest, allowing the motor to have a fixed starting direction each time it is energised by the drive circuit. Where the pole axis of the rotor refers to the dividing line between the two different poles (i.e., two magnets in this embodiment) of the rotor and the central axis of the stator pole section refers to the line passing through the center of the two pole sections 62 of the stator.

Preferably, the ratio between the distance a1 between the two oppositely spaced circumferential ends 74 of the two stator pole sections and the width a2 of the smallest air gap between the pole arc face and the rotor (in this embodiment the main air gap between the pole arc face and the rotor) is smaller than 2.

In this embodiment, the two slots 75 have uniform width and equal width and are parallel to the length direction of the branches 60. It will be appreciated that the width of each slot 75 may alternatively be non-uniform, in which case the distance a1 between the two opposing circumferential ends 74 refers to the minimum width of the slot 75.

The motor configuration of the embodiment can ensure that the rotor has a fixed starting direction, and simultaneously reduce the cogging torque of the motor, so that the rotor rotates more smoothly,

referring to fig. 8 and 9, the stator preferably includes a pair of stator windings 56 wound around respective insulated bobbins 80 that are sleeved around the two legs 60 of the stator core 54. The motor is also provided with a circuit board 82 secured to the insulating bobbin 80 in a direction substantially parallel to the branches 60. The circuit board 82 is provided with a thermal protector 84. The thermal protector 84 is disposed between the circuit board 82 and the two stator windings 56 to provide power-off protection in the event of excessive temperatures in either winding 56. The two stator windings 56 may be wound from two separate wires 86 that are disconnected and then electrically connected to each other. Each wire 86 has a respective wire inlet end 88 and wire outlet end 90, and two windings can be wound from two wires 86 simultaneously, thereby effectively saving man-hours. Two wire inlet ends 88 of the two stator windings 56 are located at one end of the two parallel branches 60 in the length direction and are located at the inner layer of the windings, and two wire outlet ends 90 are located at the other end of the two parallel branches 60 in the length direction and are located at the outer layer of the windings. The insulating bobbin 88 includes a tubular portion 92 and end walls 94 extending outwardly from opposite ends of the tubular portion 92. A winding space 95 is formed between the radially outer surface of the tubular portion 92 and the axially opposite surfaces of the end walls 94 to accommodate the winding 56. The end walls 94 of the two insulating bobbins 88 on one side of the lead-in terminal 88 are respectively provided with a wire slot 96, the two lead-in terminals 88 of the two stator windings 56 are routed to a winding space 95 on the inner side of the bobbin from the outer side of the bobbin 80 along the wire slots 96, a partition wall 98 is arranged between the wire slots 96 and the winding space 95 on the inner side of the bobbin, the partition wall 98 extends to the outer surface of the tubular part 92, the lead-in terminal 88 is blocked by the partition wall 98 until the outer surface of the tubular part 92 enters the winding space, and therefore, the lead-in terminal 88 can be separated from each layer of coil in the winding space 95, and the phenomenon that the insulating layer of the lead is scraped due to friction contact between the lead-in terminal lead and the coil in the winding space can be avoided, so that the coil is short-circuited. Preferably, the two wire terminals 90 are soldered to the circuit board 82 and electrically connected to each other such that the two windings 56 are connected in series, and the two wire terminals 88 of the two windings 56 are powered by an external single-phase ac power source. Preferably, referring to fig. 9, the two insulating bobbins 80 are integrally formed and arranged in a long strip shape along the length direction, the two windings 56 are wound on the bobbins 80, and then the two long bobbins 80 are bent into a parallel arrangement and are sleeved on the two parallel branches 60 of the stator core 54. Preferably, two wire inlets of the two windings 56 are arranged at two far ends of the two long wire frames 80 which are far away from each other or two adjacent ends of the two long wire frames 80 which are arranged in the middle of the long wire frames, and the winding directions of the two windings are the same, so that after the two wire frames are bent into parallel arrangement, the two wire inlets of the two windings are arranged at the same end, and magnetic fields generated by electrifying when the two windings are connected in series are not counteracted with each other.

Referring to fig. 10 to 12, the pump housing 14 includes a cover 100, and a base plate 102 integrally mounted with the cover 100. The cover 100 is sealingly connected to the base 102 via a sealing ring 104. Preferably, the gasket 104 is positioned within a radial recess 106 formed in the base plate 102 to prevent the gasket 104 from being removed from the base plate 102 prior to installation of the cover 100 with the base plate 102. The cover 100 includes a top panel 108 and a side wall panel 110 that connects the top panel 108 to the bottom panel 102. The inlet 16 extends generally axially outwardly from the top plate 108 and the outlet 18 extends outwardly from the side wall 110 in a generally perpendicular axial direction. The cover 100 and the bottom plate 102 form a pump chamber 12 therebetween, and the impeller 20 is rotatably provided in the pump chamber 12.

The cover body 100 and the bottom plate 102 are provided with mutually matched fastening structures, and the fastening structures can be combined together by enabling the bottom plate 102 and the cover body 102 to perform relative circumferential movement. Preferably, a circumferential extension clamping groove 112 may be provided at the outer circumferential edge of the bottom plate 102, and a circumferential extension protrusion 113 is provided at the outer surface of the cover body 100, and the axial width of the circumferential extension protrusion 113 is gradually reduced along the direction of inserting the circumferential extension clamping groove 112. The peripheral edge of the base plate 102 is further provided with an elastic arm 114 extending obliquely upwards, the free end of the elastic arm is provided with a step 116 sinking relative to the arm body, and the outer surface of the cover body 102 is provided with a bump 118. When the cover 100 is rotated in the clockwise direction, the circumferentially extending protrusions 113 of the cover 100 are inserted into the circumferentially extending catching grooves 112 of the base plate 102, and the protrusions 118 slide over the elastic arms 114. By the time the circumferentially extending projection 113 rotates into engagement with the catch 112, the tab 118 slides just to the step 116 to limit the reverse rotation of the cover 100.

The base plate 102 includes a pump chamber bottom wall 122 provided with an opening 120 and a rotor housing 124 integrally extending axially outwardly from the opening 120. A fixed end cap 126 is provided within the rotor housing 124 at an end adjacent the opening. One end of the shaft 28 passes through the end cap 126 into the pump chamber 12 to connect with the impeller 20 to drive the impeller 20 in rotation. Both ends of the shaft 28 may be supported by bearings 128 provided in the end cap 126 and bearings 130 provided at the end of the rotor housing 124 remote from the opening, respectively.

Preferably, the bearing 128 may be mounted to the end cap 126 via a vibration dampening member 132. The bearing 128 is cylindrical, the outer surface of the bearing is provided with a convex rib 134 extending along the circumferential direction, and the inner surface of the vibration damping piece 132 is provided with a groove 136 matched with the convex rib 134, so that concentricity of the bearing 128 and the rotor can be ensured. The bearing 130 may be supported by a bearing housing 138 integrally formed with the rotor housing 134, with the inner surface of the bearing housing 138 being provided with a plurality of internal teeth 140 that form a non-continuous contact with the outer surface of the bearing 130. The above configuration can reduce vibration generated when the motor is operated.

A rotor housing 124 is secured between the two stator pole sections 62 with a gap between the outer surface of the rotor 26 and the rotor housing 124 such that the rotor 26 is rotatable relative to the rotor housing 124. The rotor housing 124 has axially extending ribs 142 (shown in fig. 11) on its outer surface, and the two insulating bobbins 80 together form ribs 144 (shown in fig. 6) on two adjacent sides near one end of the stator pole sections 62, the ribs 142 and 144 respectively extending into the slots 75 between the circumferential ends 74 of the two pole sections 62 to limit relative circumferential movement of the two pole sections 62 of the stator core 54. Preferably, the outer surface of the ribs 142 on the rotor housing 124 is no higher than the side 65 of the stator pole 62 remote from the bottom 58.

Referring to fig. 11 and 13, the motor also has a motor cover 146 secured to the pump housing 14. The motor cover 146 covers the stator windings 56 and the circuit board 82 and includes a bottom wall 148 and two side walls 150 extending from the bottom wall 148. Two side walls 150 are provided on both sides of the stator core 54. The circuit board 82 is disposed between the bottom wall 148 and the stator windings 56. In this embodiment, the motor cover 146 and the pump housing 14 are fixed to each other by a snap-fit structure formed by a protrusion 152 on the side wall 150 and a hook 154 extending downward from the bottom plate 102. At least one pair of positioning protrusions 156 are provided on the bottom plate 102 at positions corresponding to the two side walls 150, and the side walls 150 are inserted between the pair of positioning protrusions 156. Preferably, the width between the pair of locating projections 156 is gradually reduced in a direction from the free ends of the projections 156 to the root, so that the pressure exerted by the side walls 150 is gradually increased until a tight fit is formed, thereby enhancing the securing force between the motor cover 146 and the pump housing 14 and reducing vibration. In this embodiment, the hooks 154 may be used as the positioning projections 156 at the same time, and it is understood that the pair of positioning projections 156 may be provided separately from the hooks 154. Preferably, the two positioning surfaces of the pair of positioning protrusions 156 are disposed in a staggered manner. It is understood that more than one pair of positioning projections 156 may be provided on each side as shown in the drawings, or only one pair of positioning projections 156 may be provided, and when more than one pair of positioning projections 156 is provided, each pair of positioning projections 156 may be provided independently of the other pairs of positioning projections 156, or a strip-shaped projection 156 may be provided on the inner side or the outer side of the side wall such that two or more pairs of positioning projections 156 share the strip-shaped projection 156.

The applicant's chinese patent applications 201410404474.2 and 201410404755.8 are incorporated herein by reference. The motor of the embodiment of the invention can ensure that the rotor rotates in the same direction in each start by matching with the driving circuit or other suitable driving circuits disclosed in any application, so that in the application of fans, water pumps and the like, the impeller driven by the rotor can adopt bent blades, thereby improving the fluid efficiency of the fans, the water pumps and the like. Under the condition of ensuring the same output, a smaller motor can be used, and energy sources are saved. The drive circuit described above may be provided on the circuit board 82 to energize the stator windings 56 in a predetermined manner based on the rotor pole position information detected by the position sensor 158 (shown in fig. 2) to ensure a fixed starting direction of the rotor each time the motor is energized. In the present embodiment, the position sensor 158 is disposed outside the rotor case 124 within an acute angle range formed by the perpendicular line of the polar axis S1 and the perpendicular line of the central axis S2 of the stator when the rotor is stationary, and is covered by the motor cover 146.

Referring to fig. 14, the impeller 20 is fixedly connected to the rotation shaft 28 to always maintain synchronous rotation with the rotation shaft 28. Impeller 20 may be made of plastic and includes a base plate 160 and a plurality of blades 162 circumferentially spaced apart from base plate 160. Preferably, the plurality of blades 162 of the impeller 20 are arcuate in shape, having two sets of long blades 164 and short blades 166, the two sets of blades being circumferentially alternately spaced about the outer periphery of the base plate 160. A spiral flow passage 168 (shown in fig. 11) is formed between the inner wall of the pump chamber 12 and the impeller 20. The area of the radial cross section of the flow passage 168 increases gradually in the circumferential direction toward the outlet 18. Under the condition that the rotor has the same rotation direction when being started each time, the fluid efficiency can be improved by adopting the arc-shaped blades and the spiral flow channels. A mounting post 170 is provided in the center of the base plate 160, and one end of the shaft 28 is fixed to the mounting post 170 via a boss 172. The sleeve 172 may be made of metal. Preferably, the end of the mounting post 170 remote from the motor in the axial direction is continuously closed from the outside to the inside by the mounting post 170, the sleeve 172, and the injection molded portion 174. Injection molded portion 174 is connected to mounting post 170 via bridge portion 176. It will be appreciated that the impeller 20 may also employ straight blades.

The pump 10 provided by the invention is particularly suitable for being used as a drainage pump of a washing device such as a dish washer, a washing machine and the like. Fig. 15 illustrates a dishwasher 176 having a drain pump according to a preferred embodiment of the present invention, including a washing chamber 178, a water supply passage 180 supplying washing water to the washing chamber 178, a drain passage 182 discharging the washing water to the outside, a circulation passage 184 circulating the washing water in the washing chamber 178, and a control system 188 having the drain pump 10 and a circulation pump 186. Wherein the drain pump 10 pumps the washing water in the washing chamber 178 to the drain passage 182, and the circulation pump 186 pumps the washing water in the washing chamber 178 to the circulation passage 184.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims

1. The synchronous motor comprises a stator and a permanent magnet rotor capable of rotating relative to the stator, wherein the rotor comprises a rotating shaft and two magnets fixed on the rotating shaft, each magnet circumferentially covers half of the circumference and is provided with a radial outer surface, a radial inner surface and two connecting surfaces respectively connected with the radial outer surface and the radial inner surface at two sides, the radial outer surface comprises a cambered surface part, and the radial inner surfaces of the two magnets jointly form an inner hole for the rotating shaft to pass through; the stator comprises a stator magnetic core and a stator winding wound on the stator magnetic core, wherein the rotor runs at a constant speed at a rotating speed of 60f circles/min in a steady-state stage when the stator winding is connected with an alternating current power supply in series, wherein f is the frequency of the alternating current power supply; the stator magnetic core is provided with two opposite pole parts and a yoke part connected with the two pole parts, each pole part is provided with a pole arc surface opposite to the rotor, and an air gap is formed between the pole arc surface and the rotor; the ratio between the polar arc angle of the magnet and 180 degrees is 0.75-0.95, the radial outer surface of the magnet further comprises a plane part extending from two circumferential ends of the cambered surface part to the connecting surface, the radial outer surfaces of the two magnets are arranged in a coplanar mode on two plane parts on the same side, and the distance between the circumferential ends of the two plane parts is 2 mm-9.5 mm.

2. The synchronous machine of claim 1 wherein the two poles have circumferential ends disposed in spaced relation to one another.

3. A synchronous machine as claimed in claim 2, characterized in that the ratio between the distance between the circumferential ends of the gap and the smallest width of the air gap is smaller than 2.

4. The synchronous machine of claim 1 wherein the pole segments are concentric with the rotor to form a primary air gap of equal spacing therebetween; the arc surface is provided with a concave starting groove, and uneven air gaps with unequal intervals are formed between the starting groove and the rotor.

5. The synchronous motor of claim 1, wherein the two magnets are fixed on the rotating shaft by an overmoulding piece, the outer surface of the overmoulding piece is concentric with the rotating shaft, two connecting surfaces of the magnets are coplanar, and the ratio between the length of two ends of the two connecting surfaces and the diameter of the outer surface of the overmoulding piece is between 0.82 and 0.95.

6. The rotor comprises a rotating shaft and two magnets fixed on the rotating shaft, wherein each magnet circumferentially covers half of the circumference and is provided with a radial outer surface, a radial inner surface and two connecting surfaces respectively connected with the radial outer surface and the radial inner surface at two sides, the radial outer surface comprises a cambered surface part, and the radial inner surfaces of the two magnets jointly form an inner hole for the rotating shaft to pass through; the ratio between the polar arc angle of the magnet and 180 degrees is 0.75-0.95, the radial outer surface of the magnet further comprises a plane part extending from two circumferential ends of the cambered surface part to the connecting surface, the radial outer surfaces of the two magnets are arranged in a coplanar mode on two plane parts on the same side, and the distance between the circumferential ends of the two plane parts is 2 mm-9.5 mm.

7. The rotor of claim 6, wherein the ratio of the pole arc angle of the magnet to 180 degrees is between 0.9 and 0.95.

8. The rotor of claim 6, wherein the two magnets are fixed to the shaft by an overmold, an outer surface of the overmold is concentric with the shaft, two connection faces of the magnets are coplanar, and a ratio between a length of two ends of the two connection faces and a diameter of the outer surface of the overmold is between 0.82 and 0.95.

9. A rotor according to claim 6, wherein the distance between the two circumferential ends of the two planar portions is between 2mm and 2.5 mm.

10. The rotor of claim 6, wherein the two magnets are fixed to the rotating shaft by an over-mold member, the radially outer surfaces of the magnets further include planar portions extending from both circumferential ends of the arcuate portions to the connection face, the radially outer surfaces of the two magnets are disposed coplanar at both planar portions on the same side, and the over-mold member is provided with a positioning groove provided at the connection of the two magnets and entirely covering the two planar portions in the circumferential direction.

11. An electrical machine comprising a stator and a rotor as claimed in any one of claims 6 to 10.

12. A pump, comprising:

a pump housing having a pump chamber;

an inlet and an outlet in communication with the pump chamber;

an impeller disposed within the pump chamber; and

a motor for driving the impeller, the motor comprising a stator and a rotor rotatable relative to the stator, the rotor having the features of the rotor of any one of claims 6 to 10.

13. A cleaning device comprising: a washing chamber, a water supply passage supplying washing water to the washing chamber, a drain passage discharging the washing water to the outside, and a drain pump pumping the washing water in the washing chamber to the drain passage; wherein the drain pump has the features of the pump of claim 12.