AU2014100416A4

AU2014100416A4 - Food processor

Info

Publication number: AU2014100416A4
Application number: AU2014100416A
Authority: AU
Inventors: Shiwen Wang; Hongliang Yi; Jun Zhang
Original assignee: Johnson Electric SA
Current assignee: Johnson Electric SA
Priority date: 2013-04-24
Filing date: 2014-04-24
Publication date: 2014-05-29
Anticipated expiration: 2022-04-24
Also published as: CN105361740A; DE202014101885U1; CN104124822A

Abstract

A food processor 10 has a base 12, a container 14 mounted on the base for containing food, a rotatable work piece 16 for processing food inside the container, and an electric motor 20 for driving the work piece. The electric motor 20 includes a stator and a rotor. The stator has a stator core 22 and stator windings 26 that are wound about the stator core. The rotor is rotatably mounted with respect to the stator and has a shaft 34, a rotor core 36 fixed to the shaft 34, and a plurality of permanent magnets 38 that are embedded in the rotor core. The work piece 16 is arranged coaxially with the shaft 34. Figure 1 SHEET 1 of 3

Description

- 1 Food Processor FIELD OF THE INVENTION [0001] This invention relates to electrical domestic appliances and in particular, to an electric motor used to drive a kitchen appliance, such as a food processor. BACKGROUND OF THE INVENTION [0002] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. [0003] A food processor, such as a dough maker, requires a low speed for mixing foods of high viscosity, such as when mixing flour for making bread. Such function often requires a rotating speed of several tens or several hundreds of revolutions per minute of the work piece or mixer and a relatively large torque. Traditionally, it is common practice to add a step down gear mechanism between the electric motor and the mixer in order to obtain a lower rotating speed and a larger torque than provided direction from the motor. Not only the cost is high, but the size of the food processor is also large. For food processors having more than one speed, such as a high speed for mixing liquids etc., the step down gear mechanism may be a source of additional noise. SUMMARY OF THE INVENTION [0004] The present invention is aimed at providing a new type of food processor that overcomes the abovementioned problem or at least provides a useful choice. [0005] Accordingly, in one aspect thereof, the present invention provides a food processor comprising: a base, a container mounted on the base for containing food, a rotatable work piece for processing the food inside the container, and an electric motor for driving the work piece, wherein the electric motor includes a stator and a rotor rotatably mounted with respect to the stator; the stator includes a stator core and stator windings that are wound about a plurality of teeth of the stator core, and the rotor includes a shaft, a rotor core that is fixed to the shaft, and a plurality of permanent magnets that are embedded in the rotor core.

-2 [0006] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". [0007] Preferably, the work piece is arranged coaxially with the shaft. [0008] Preferably, the food processor has at least a high-speed working mode and a low speed working mode, wherein the speed of the electric motor under the high-speed working mode is 20-600 times the speed of the electric motor under the low-speed working mode. [0009] Preferably, the food processor has at least a low-speed working mode, and the speed of the electric motor under said low-speed working mode is between 25 and 200 rpm. [0010] Preferably, the food processor also has a high-speed working mode, and the speed of the electric motor under the high-speed working mode is between 4000 and 15000 rpm. [0011] Preferably, the maximum output torque of the electric motor under the low-speed working mode is 4 Nm. [0012] Preferably, the number of magnetic poles formed by the plurality of permanent magnets is 2N, and the number of teeth of the stator core is 3M, wherein N is an integer greater than or equal to 3, and M is an integer greater than 3. [0013] Preferably, the number of permanent magnets is greater than or equal to 4N. [0014] Preferably, the electric motor is an 8-pole/1 2-slot or a 10-pole/1 2-slot electric motor. [0015] Preferably, the axial length of the rotor core is between 20mm and 50mm. [0016] In the food processor of the present invention, there is no need for adding a gear mechanism between the motor and the work piece and the shaft is directly coupled to the work piece, thereby reducing the cost of the food processor and also bringing about advantages of minimization of the product size. Furthermore, the food processor also runs smoothly under the low-speed working mode, producing less noise. Additionally, as the permanent magnets -3 are embedded inside the rotor core, the separation of magnets from the rotor core due to the centrifugal force under the high-speed working mode may be prevented. BRIEF DESCRIPTION OF THE DRAWINGS [0017] A preferred embodiment of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labelled with a same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. [0018] Fig. 1 depicts a partially exploded view of a food processor according to the preferred embodiment of the present invention; [0019] Fig. 2 depicts an electric motor of the food processor of Fig. 1; [0020] Fig. 3 is a sectional view of the electric motor of Fig. 2; [0021] Fig. 4 is a top view of the electric motor of Fig. 2, with a part removed; and [0022] Fig. 5 is a plan view of a rotor lamination, being a part of the electric motor of Fig. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0023] Referring to Fig. 1, according to the preferred embodiment of this invention, the food processor 10 comprises a base 12, a container 14 that is mounted on the base 12 for containing food, a rotatable work piece 16 for processing the food inside the container 14, and a built-in permanent magnet brushless motor 20 (not shown in Fig. 1) for driving the work piece 16. The motor 20 is disposed within the base. The work piece may be a cutting blade, a mixing head, etc. [0024] Referring to Figures 2 to 5, the built-in permanent magnet brushless motor 20 includes a stator and a rotor. The rotor is rotatably mounted with respect to the stator. The stator includes a stator core 22, stator windings 26 that are wound about teeth 24 of the stator core and two end brackets 28, 30 installed on the axial ends of the rotor core. The stator core -4 22 is constructed from a plurality of stator laminations made from a magnetic material (such as iron or electrical steel) and stacked in the axial direction of the motor. The stator laminations form an annular yoke 23 and 12 teeth 24 that extend inwardly from the yoke 23. The stator windings 26 include 12 coils. Each coil is wound around the body of a corresponding tooth 24 and each tooth forms a salient pole. The stator core 22 is fixed between the two end brackets 28, 30 by screws 32. [0025] The rotor includes a shaft 34, a rotor core 36 fixed to the shaft 34, permanent magnets 38 embedded inside the rotor core 36, and two balancing rings 40 positioned respectively at the axial ends of the rotor core 36. The shaft 34 is rotatably supported by two bearings mounted respectively on the end brackets 28, 30. The shaft 34 is arranged coaxially with the work piece 16, and is detachably coupled directly to the work piece such that the work piece rotates with the shaft 34, without any speed reduction mechanism. The balancing rings 40 are used to balance the rotor. [0026] The rotor core 36 is constructed from a plurality of rotor laminations made from a magnetic material (such as iron or electrical steel) and stacked in the axial direction of the motor. Each rotor lamination has a plurality of first apertures 44 and a plurality of second apertures 46. The first apertures are equal-angularly spaced about a circle coaxial with the axis of the rotor and spaced from the radially outer edge of the lamination. The second apertures are also equal-angularly spaced about the lamination and are partially open through the radially outer edge of the lamination. The first and second apertures are alternately disposed in the circumferential direction of the lamination. Thus the first and second apertures form grooves or passages extending axially through the rotor core 36. [0027] The permanent magnets 38 include first permanent magnets 48 embedded in the passages formed by the first apertures 44 and second permanent magnets 50 embedded in the passages formed by the second apertures 46. The first permanent magnets 48 and second permanent magnets 50 may be made from the same material, preferably such as ferrite. The radially outer sides of the passages formed by the second apertures are non enclosed, and the radially outer peripheral edge 52 of the rotor core 36 extends into the passages formed by the second apertures 46 and touches against the radially outer surface of the second permanent magnets 50.

-5 [0028] In this embodiment, each first permanent magnet 48 has opposite magnetic poles on the two radial surfaces, and each second permanent magnet 50 has the opposite magnetic poles on the two circumferential surfaces. The two circumferential surfaces facing each other from two adjacent second permanent magnets 50 share the same magnetic polarisation with the radially outer surface of the first permanent magnet 48 positioned between these two second permanent magnets 50, thereby forming 8 magnetic poles on the rotor. The 12 teeth of the stator form 12 stator poles with each tooth supporting a single coil. The stator poles are also referred to as slots due to the slots formed between the teeth to accommodate the coils. In other words, the electric motor 20 is an 8-pole/1 2-slot electric motor. It must be understood that the motor 20 may also have other configurations. For example, preferably, a 10-pole/1 2 slot embedded permanent magnet brushless motor may be used to replace the aforesaid 8 pole/1 2-slot motor. Also, the embedded permanent magnets 38 of the rotor may also be configured by other methods, for instance instead of the 2N magnetic poles being formed by 4N magnets as described in the above embodiment, they may be formed by 6N magnets. Alternatively, embedded permanent magnet motors of other appropriate pole-slot configurations may also be used. For example, permanent magnets of the rotor form 2N magnetic poles together with a stator core having 3M teeth, wherein N is an integer greater than 3 and M is an integer greater than 3. [0029] Preferably, the axial length of the rotor core is from 20 to 60mm, more preferably it is between 20 and 50mm. [0030] The food processor of this embodiment has at least a low-speed working mode. The preferred rotational speed of the motor under the low-speed working mode is from 25 to 200 rpm (revolutions per minute), and the maximum output torque of the motor may reach 4 Nm, so that it is possible to mix foods of a higher viscosity. More preferably, the motor 20 has a variable speed, so that the food processor has at least one high-speed working mode and one low-speed working mode, wherein the motor speed under the high-speed working mode is 20 - 600 times the motor speed under the low-speed working mode. In a more preferred embodiment, the speed of the motor under the high-speed working mode is between 4000 and 15000 rpm, and the output torque of the motor is no greater than 2 Nm, so that it is possible to mix or crush foods of a lower viscosity; whereas the rotating speed of the motor under the low speed working mode is from 25 to 200 rpm and the output torque of the motor can reach 4 Nm, so that it is possible to mix foods of a higher viscosity.

-6 [0031] Food processors according to the present invention do not require a gear mechanism between the motor and the work piece to change the operating speed of the work piece. The shaft is directly coupled to the work piece, thereby reducing the cost of the food processor and enabling the size of the food processor to be reduced. Furthermore, the closer arrangement of the permanent magnets in the embedded permanent magnet brushless motor enables a smaller fluctuation in the output torque of the motor, thus the food process may run smoothly and have a low noise level even under the low-speed working mode. Additionally, as the permanent magnets are embedded inside the rotor core, the separation of magnets from the rotor core due to the centrifugal force under the high-speed working mode may be prevented. [0032] In the description and claims of the present application, each of the verbs "comprise", "include", "contain" and "have", and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items. [0033] Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.

Claims

1. A food processor comprising: a base, a container mounted on the base for containing food, a rotatable work piece for processing the food inside the container, and an electric motor for driving the work piece, wherein the electric motor includes a stator and a rotor rotatably mounted with respect to the stator; the stator includes a stator core having a plurality of teeth and stator windings wound about the teeth, and the rotor includes a shaft, a rotor core fixed to the shaft, and a plurality of permanent magnets embedded in the rotor core.

2. A food processor according to Claim 1, wherein the work piece is arranged coaxially with the shaft.

3. A food processor according to Claim 1 or 2, wherein the food processor has at least a high-speed working mode and a low-speed working mode, wherein the speed of the electric motor under the high-speed working mode is 20-600 times the speed of the electric motor under the low-speed working mode.

4. A food processor according to Claim 1 or 2, wherein the food processor has at least a low-speed working mode, and the speed of the electric motor under said low-speed working mode is between 25 and 200 rpm.

5. A food processor according to Claim 4, wherein the food processor also has a high speed working mode, and the speed of the electric motor under the high-speed working mode is between 4000 and 15000 rpm.

6. A food processor according to Claim 3 or 4, wherein the maximum output torque of the electric motor under the low-speed working mode is 4 Nm.

7. A food processor according to any one of the preceding claims, wherein the number of magnetic poles formed by the plurality of permanent magnets is 2N, and the number of teeth of the stator core is 3M, wherein N is an integer greater than or equal to 3, and M is an integer greater than 3.

8. A food processor according to Claim 7, wherein the number of permanent magnets is greater than or equal to 4N. -8

9. A food processor according to any one of the preceding claims, wherein the electric motor is an 8-pole/1 2-slot or a 10-pole/1 2-slot electric motor.

10. A food processor according to any one of the preceding claims, wherein the axial length of the rotor core is between 20 mm and 50mm.

11. A food processor substantially as herein before described with reference to the accompanying drawings.