EP1557566A1

EP1557566A1 - Centrifugal pump for washing apparatus

Info

Publication number: EP1557566A1
Application number: EP04001620A
Authority: EP
Inventors: Kouichi Sadakane
Original assignee: Nidec Shibaura Corp
Current assignee: Nidec Shibaura Corp
Priority date: 2004-01-26
Filing date: 2004-01-26
Publication date: 2005-07-27
Anticipated expiration: 2024-01-26
Also published as: DE602004005297T2; DE602004005297D1; EP1557566B1

Abstract

A pump (1) of the present invention includes a circular stator (10) at the outside of a peripheral wall of a casing (41). A pump chamber (20) is formed inside the casing (41). Furthermore, a circular rotor magnet (24) is arranged inside the casing that faces with the stator (10) in the radial direction with a radial gap , and a peripheral wall of the casing (41) is located in between the radial gap. The rotor magnet (24) is fixed to an impeller (27) integrally and is supported in the pump chamber (20) in a rotatable manner. An end of the casing (41) is opened so as to form an inlet (21) that communicates with the pump chamber (20). In addition, the other end of the casing (41) is sealed with a bottom plate (42). A part of the peripheral wall that is close to the sealed end of the casing (41) is opened and connected to a delivery pipe (45) so as to open to an outlet (22). Thus, a small size, a low cost and a long life of the pump (1) are achieved. In addition, the pump (1) having this structure is used for a washing apparatus, e.g., a dishwasher (2) so that the entire apparatus can be realized with a small size and a low cost.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump that intakes and ejects a liquid, and a washing apparatus using the pump. Especially, a pump of the present invention has a structure in which an impeller disposed within a pump chamber and a motor portion for rotating the impeller make a unit so that a small size, a low profile, a low weight and a low cost can be realized. In addition, a washing apparatus of the present invention is manufactured using a pump of the present invention so as to realize a small size.

2. Description of the Prior Art

Many types of washing apparatus use pumps. Such the washing apparatus in which a pump inside is used in an ordinary household , e. g. ,a dishwasher. Therefore, a compact sizes, a low price and easy operation are requested for the washing apparatus in the market. Accordingly, a pump that is mounted in the apparatus is also required to be a compact size and a lightweight and is available in a low cost.
As a conventional pump, there is one that is described in Japanese unexamined patent publication No. 2003-106285, for example. This pump has a structure in which one of magnet couplings is attached to a shaft of an electric motor for rotating an impeller and the other magnet coupling is attached to the impeller that is covered with a casing, so that a rotational force of the electric motor is transmitted to the impeller located in the casing via a magnetic coupling force of the magnet coupling and the impeller is rotated for transferring a liquid.
Furthermore, as another pump, there is one that is described in Japanese unexamined patent publication No. 11-32962, for example. This pump has a structure in which an impeller is attached directly to an output shaft of an electric motor, and this impeller is covered with a casing, so that the impeller is rotated directly by the rotation of the electric motor for transferring a liquid.
However, since the electric motor portion and a pump region portion including the impeller are arranged in the axial direction in each of the above-explained conventional pumps, it is difficult to shorten a length of the entire pump in the axial direction. Especially, the pump described in Japanese unexamined patent publication No. 2003-106285 has a disadvantage that a lot of components are necessary since the shaft of the electric motor and the shaft of the impeller have to be coupled to each other by a magnet coupling on the axis. In addition, the pump described in Japanese unexamined patent publication No. 11-32962 has a drawback that although the impeller can be attached directly to the output shaft of the electric motor, some seal structures must be equipped between the casing and the output shaft.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a pump with a small size, especially a length in an axial direction so as to realize a low-profile.
The second object of the present invention is to provide a pump with a lightweight and a low cost by reducing the number of components.
The third object of the present invention is to provide a pump that can adjust a flow rate by controlling the revolution speed of the motor.
In addition, another object of the present invention is to provide a washing apparatus having small size, a low profile, a light weight, a high performance and a low cost by utilizing a pump in which the above-mentioned three objects are achieved.
A pump according to the present invention includes a pump casing defining a pump chamber inside, an inlet and an outlet that are provided to the pump casing, an impeller that is arranged in the pump chamber and a motor for rotating the impeller. When the impeller is rotated, a fluid is fed from the inlet to the outlet through the pump chamber. The pump casing of this pump includes a substantially cylindrical peripheral wall having one end that is open as the inlet and the other end that is sealed. In addition, the outlet is formed on a side face of the peripheral wall. The motor that rotates the impeller includes a circular stator that is arranged at the outside of the peripheral wall. A circular rotor magnet faces with the stator in the radial direction with a radial gap, and the peripheral wall is located in between the radial gap. In addition, the rotor magnet is fixed to a peripheral portion of the impeller integrally.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure:
Fig. 1 is a cross section of a pump according to a first embodiment of the present invention; and
Fig. 2 is a cross section of a joint portion between the dishwasher and the pump in a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a pump and a washing apparatus using the pump according to the present invention shall be explained with reference to drawings.
Fig. 1 is a vertical cross section of the pump 1 according to a first embodiment.
In the following explanation of the first embodiment, expression about the vertical direction corresponds to the vertical direction shown in Fig. 1 as a matter of convenience unless a special description is made. However, in a practical embodiment, the direction is not limited to this embodiment.
The pump 1 includes a substantially cylindrical stator 10. The stator 10 includes a stator core 11 in which a plurality of polar teeth is arranged to be directed to the inner direction, a stator coil 12 that is turned around each of the polar teeth of the stator core 11 and a circuit board 13 on which a motor driving circuit is mounted for controlling current supply to the stator coil 12. This circuit board 13 is disposed at the upper end or the lower end of the substantially cylindrical stator core 11 and the stator coil 12. This stator 10 is covered with a molding material 14 that has insulating properties. This molding material is a synthetic resin that has insulating properties, and it also has good water resisting properties. A pump is usually used in a humid and an easily submerged environment. Since the stator is covered with the molding material, insulating properties and water resisting properties of the stator 10 can be improved, so that a long life and a high durability of the pump can be realized.
At the inner circumference of the stator 10, there is a peripheral wall that is a part of the casing 41 and a pump chamber 20 that is formed in the peripheral wall. The casing 41 includes an upper casing 41A made of a resin that has openings at both ends in the vertical direction and a lower casing 41B made of a stainless steel sheet for closing the lower end opening of the upper casing 41A. In addition, an O ring 42 is disposed at the fastening portion between the upper casing 41A and the lower casing 41B, which are fastened by a screw 43 so that water proofing property is improved.
The upper casing 41A includes a substantially cylindrical upper peripheral wall portion 41A1, a lower peripheral wall portion 41A2 that is disposed continuously to the lower end of the upper peripheral wall portion 41A1 and has diameter larger than the upper peripheral wall portion 41A1, a connection opening portion 41A3 that is formed on the outer side face of the lower peripheral wall portion 41A2 in a continuous manner, and a tube-like delivery pipe 41A4 that is connected to the connection opening portion 41A3 and is drawn outward. The upper peripheral wall portion 41A1 and the lower peripheral wall portion 41A2 constitute a ring-like peripheral wall that forms the pump chamber 20. The upper end of the peripheral wall is opened so as to form the inlet 21, while the lower end of the peripheral wall is sealed with the lower casing 41B. A part of the lower side face of the peripheral wall is connected to the delivery pipe 41A4 via the connection opening portion 41A3, and the outer end portion of the delivery pipe 41A4 is opened to form the outlet 22.
The above-explained stator 10 engages the outer surface of the upper peripheral wall portion 41A1, and the lower face of the stator 10 abuts a ring-like flat portion that is disposed between the upper peripheral wall portion 41A1 and the lower peripheral wall portion 41A2 so as to link them. In addition, a delivery chamber 20B is positioned beneath the stator 10.
The lower casing 41B that seals the lower end of the peripheral wall (that includes the upper peripheral wall portion 41A1 and the lower peripheral wall portion 41A2) is made of a stainless steel sheet. Compared with the upper casing 41A that has a solid structure, the lower casing 41B has a flat shape and is required to have sufficient strength. A stainless steel sheet has sufficient mechanical intensity compared with a resin, so even if a thickness of the lower casing 41B is decreased, an intensity that is sufficient for enduring a pressure inside the pump chamber 20 can be secured. In addition, a stainless steel sheet has high anti-corrosion characteristics compared with a usual steel material, for example. Therefore, it is hardly eroded even in a liquid in which salt, oil or detergent is dissolved, in a hot liquid such as a hot water or in a humid atmosphere after water is drained.
Furthermore, this lower casing 41B can be made of other metals than the stainless steel sheet, such as various steel sheets that have enough strength to endure a pressure inside the pump chamber 20 and are faced with anti-corrosion characteristic, an aluminum and an alloy including an aluminum as a main ingredient, an alloy such as a brass including copper and zinc as main ingredients, or other metals that have anti-corrosion characteristics. A reinforced resin can be used depending on operating temperature and a type of fluid.
A rotating member 23 is disposed in the pump chamber 20 in a rotatable manner. The rotating member 23 includes an impeller 27, a rotor magnet 24 and a bearing mechanism.
At the rotation center of the rotating member 23, there is a fixed shaft 30 that is arranged to stand on the lower casing 41B, and the fixed shaft 30 is inserted through a cylindrical bearing 33 that is disposed at the middle portion of the impeller 27 to that a slide bearing is constituted. In this way, the impeller 23 is supported by the fixed shaft 30 in a rotatable manner. The fixed shaft 30 is fixed to the lower casing 41B by inserting one end of the fixed shaft 30 in the through-hole of the lower casing 41B and by fastening a box nut 36 from the opposite side thereof via an O ring 35. In addition, a thrust washer 31 is engaged with the other end of the fixed shaft 30 so as to prevent the bearing 33 from dropping out. Since the fixed shaft 30 is fixed only at one end, it is not necessary to insert an arm for supporting the other end of the fixed shaft 30 in the pump chamber. As a result, resistance of a fluid that flows in the pump chamber 20 can be reduced. In addition, since this bearing 33 is made of a bearing metal that does not need lubricating oil. Accordingly, relatively simple and low-cost structure can be realized without a complicated seal structure.
Instead of the slide bearing that is used in this embodiment, a slide bearing in which a rotation shaft is inserted in and supported by a fixed bearing, a slide bearing that has a sealing structure for using lubricant or a ball bearing can be used.
The impeller 27 is a centrifugal type impeller having a substantially conical impeller base 27A and a plurality of blades 27B arranged on the upper surface of the impeller base 27A in the circumferential direction.
The rotor magnet 24 has a circular shape and is provided integrally so as to link outer periphery rims of the plural blades 27B outside of the impeller 27. The rotor magnet 24 includes a plurality of magnetic poles that are arranged in the circumferential direction and are magnetized in the radial direction. The rotor magnet 24 faces with the stator 10 in the radial direction with a radial gap , and the upper peripheral wall portion 41A1 is located in between the radial gap, and the stator 10 engages the outer portion of the upper peripheral wall portion 41A1. This rotor magnet 24 is made of a plastic magnet. The plastic magnet is easily formed into a complicated shape compared with a sintered magnet or a cast magnet. In addition, since the rotor magnet 24 is a plastic magnet, it is possible to weld and fix the rotor magnet 24 with the impeller 27 if it is made of a resin. In this case, the rotor magnet 24 is hardly dropped off from the impeller 27 during a long period of use, compared with the case where they are bonded to each other with an adhesive or a fit-in process.
Furthermore, for a small size a magnet having more magnetic flux density, e.g., a sintered rare earth magnet may be used.
There is a possibility that the rotor magnet 24 may be corroded in water containing salt or oil and fat content since it contains a ferromagnetic metal. Therefore, the surface thereof is covered with a film that is magnetically transparent and has anti-corrosion characteristics.
The lower end of the rotor magnet 24 faces the lower end of the upper peripheral wall portion 41A1. A gap is formed between the lower end of the rotor magnet 24 and the upper face of the peripheral portion of the impeller base 27A in the axial direction, and the gap faces with the delivery chamber 20B. Thus, when the impeller 27 rotates, fluid in the vicinity of the inlet 22 is taken in the pump chamber 20 through the upper portion of the impeller 27, passes through the gap between the rotor magnet 24 and the impeller base 27A, is ejected to the lower outer periphery of the impeller 27, and is led to the delivery chamber 20B.
The rotor magnet 24 that is a part of the rotating member 23 and the stator 10 constitute a brushless DC motor. When a direct current is supplied to the motor driving circuit on the circuit board 13, the current is controlled by the motor driving circuit in accordance with a rotation state and is supplied to the stator coil 12. In addition, this motor driving circuit can control the motor by receiving a signal from the outside of the motor, e.g., a control circuit of an apparatus in which the pump is embedded. In this way, the motor can be controlled in accordance with a flow rate that is required to the apparatus.
Furthermore in this embodiment, this motor is not limited to a brushless DC motor. For example, it is possible to use an induction motor or an AC servo motor.
In the pump 1 having the structure as explained above, when a current is supplied to the stator coil 12 first, the stator coil 12 is energized, the poles of the stator core 11 form magnetic poles, the rotor magnet 24 generates a rotation force due to an electromagnetic interaction with the magnetic poles of the rotor magnet 24, and the rotor magnet 24 rotates together with the impeller 27. When the impeller 27 rotates, a turning flow is generated along the circumferential direction of the impeller 27 in the pump chamber 20. Then the rotation of the impeller 27 leads the fluid to the lower end outer periphery (the delivery chamber 20B) of the impeller 27 via the gap between the rotor magnet 24 and the impeller base 27A. Further, the fluid in the delivery chamber 20B is gathered in the confluent chamber 20C, is led to the delivery pipe 41A4 and ejected from the outlet 22. In this way, the rotation of the impeller 27 that is united with the brushless DC motor transmits the fluid from the inlet 21 to the outlet 22.
The pump 1 in this embodiment that is explained above as the present invention has a structure in which the rotor magnet 24 that constitutes a part of the motor is disposed at the peripheral portion of the impeller 27 integrally, and the pump portion and the motor portion is integrated. Therefore, the pump can be a low profile type without deteriorating the performance, so that an apparatus in which the pump is used can be downsized as a whole. Moreover, a weight of the pump can be reduced, and the cost of the pump can be also reduced. In addition, durability of the pump over a long period can be improved.

(Second embodiment)

A second embodiment is a washing apparatus to which the pump 1 that is explained in the first embodiment in detail is attached. Especially, a dishwasher that is used widely in ordinary households is exemplified for the explanation. Fig. 2 is a general vertical cross section showing a joint portion between the pump 1 in the second embodiment and a water tank 50 in a dishwasher 2 that utilizes the pump 1.
In the following explanation of the second embodiment, expression about the vertical direction corresponds to the vertical direction shown in Fig. 2 as a matter of convenience unless a special description is made. However, in a practical embodiment, the direction is not limited to this embodiment.
The dishwasher 2 includes a washing chamber for housing dishes (not shown) and a water tank 50 for storing wash water that is used for washing dishes or waste water after washing. Wash water 61 that is stored in the water tank 50 before washing is taken in the pump 1 from the water tank 50 and is sent to the washing chamber. In addition, waste water 62 that was recovered in the water tank 50 after washing is taken in the pump 1 from the water tank 50 and is ejected to the outside of the apparatus.
The lower end of the water tank 50 of the dishwasher 2 is provided with a connection opening portion 53, which is connected to the inlet 21 of the pump 1. A net 58 is disposed at the vicinity of the connection opening portion 53 for collecting garbage that was dropped off the dishes when being washed. The peripheral surface of a connection pipe 52 and the inner circumferential surface of the upper peripheral wall portion 41A1 of the pump are connected via an O ring 57. In addition, the upper end of the pump 1 abuts the bottom surface 54 of the water tank 50 for registration, so that a rattling state when installing the pump 1 in an apparatus can be suppressed.
In addition, the delivery pipe 41A4 of the pump 1 is connected to a switching valve (not shown). The switching valve has two switching ports. One port is connected to the washing chamber, and the other port is connected externally. By switching the switching valve, an operation for feeding wash water 61 to a washing chamber and another operation for draining the waste water 62 externally can be switched. Furthermore, a structure and a driving method of this dishwasher 2 are similar to a structure and a driving method of a general dishwasher, so explanation of them is omitted.
The washing apparatus or the dishwasher having the structure of the present invention realizes a small size and a low cost of the apparatus by using the compact and low profile pump 1. In addition, by improving the method of installing the pump in the apparatus, further cost reduction is achieved and problems including vibration and noise are reduced.
Furthermore, although a dishwasher is exemplified for explaining the case where the present invention is applied to a washing apparatus in the above embodiment, the pump 1 of the present invention can be also applied to a washing machine, a water heater, a water circulation apparatus for a bath, or other washing apparatus using water, or other various fluid circulation and supplying apparatus, so as to contribute to downsizing, weight reduction or cost reduction of them.

Claims

A pump comprising:

a pump casing defining a pump chamber inside;

an inlet that is provided to the pump casing and is communicated with the pump chamber;

an outlet that is provided to the pump casing and is communicated with the pump chamber;

an impeller that is arranged in the pump chamber in a rotatable manner;

a motor portion for rotating the impeller, and

the impeller being rotated so that the pump takes a fluid into the pump chamber through the inlet and ejects the fluid through the outlet, wherein

the pump casing includes a substantially cylindrical peripheral wall having one end that is open as the inlet and the other end that is sealed,

the peripheral wall defines the pump chamber inside,

the outlet is formed on the peripheral wall, and

the motor portion includes a circular stator that is arranged at the outside of the peripheral wall substantially in a coaxial manner, and a circular rotor magnet that is fixed to a peripheral portion of the impeller integrally so as to face with the stator in the radial direction with a radial gap , and the peripheral wall is located in between the radial gap , and

the motor portion is driven so as to apply a rotational force directly to the impeller.
The pump according to claim 1, wherein the stator includes a plurality of polar teeth that are directed inwardly and are arranged in the circumferential direction, and the rotor magnet includes a plurality of magnetic poles that are directed in the radial direction and are arranged in the circumferential direction.
The pump according to claim 1 or 2, wherein the impeller is a centrifugal type impeller in which a plurality of blades are arranged on the peripheral surface of a substantially conical base in the circumferential direction, and the rotor magnet is fixed to the outer periphery of the impeller in an integral manner so as to form a gap in the axial direction with the outer periphery of a bottom portion of the base.
The pump according to any one of claims 1-3, wherein the peripheral wall of the pump casing includes a cylindrical wall that faces the peripheral surface of the rotor magnet of the impeller and forms an opening end portion of the peripheral wall, and a large diameter wall that has a diameter larger than the cylindrical wall and forms a sealing end portion of the peripheral wall, the cylindrical wall and the large diameter wall are connected to each other continuously, and a part of the large diameter wall is provided with the outlet.
The pump according to any one of claims 1-4, wherein the sealing end portion of the peripheral wall is sealed with a bottom plate, which is made of a metal having anti-corrosion characteristics.
The pump according to any one of claims 1-5, wherein the sealing end portion of the peripheral wall is sealed with a bottom plate, which is provided with a bearing portion for supporting the impeller in a rotatable manner.
The pump according to any one of claims 1-6, wherein the stator includes a stator core having a plurality of polar teeth, a stator coil that is turned around the polar teeth of the stator core, and a circuit board constituting a circuit for controlling current supply to the stator coil, which are covered with a molding material having insulating properties.
The pump according to any one of claims 1-7, wherein a surface of the rotor magnet is covered with a film having anti-corrosion characteristic.
A washing apparatus comprising a washing chamber in which objects to be washed are housed and washed, a water tank for storing wash water that is used for washing or waste water after washing, and a pump according to any one of claims 1-8, wherein the inlet of the pump is connected to the water tank.