WO2019020358A1

WO2019020358A1 - Electric motor and ship propulsion device

Info

Publication number: WO2019020358A1
Application number: PCT/EP2018/068577
Authority: WO
Inventors: Ning Jiang; Li Cheng ZHANG; Rui Chun DUAN; Da Wei LIU; Wil Van Mol; Fu Hua QIU
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-07-24
Filing date: 2018-07-09
Publication date: 2019-01-31
Also published as: CN109301973B; CN109301973A

Abstract

The present invention provides an electric motor and a ship propulsion device provided with the electric motor. The electric motor comprises: a stator (473); a rotor (471) which is rotatably provided on a motor shaft (470); and a housing structure (44) which comprises a housing extending in an axial direction of the electric motor and surrounding the stator of the electric motor, and at least one heat dissipation strip (441) which is provided and attached between an inner side surface of the housing facing the stator and an outer surface of the stator of the electric motor.

Description

Specification

Electric motor and ship propulsion device

Technical Field

The present invention relates to an electric motor, in particular to an electric motor for a ship propulsion device. In addition, the present invention also relates to a ship propulsion device, in particular to a podded propulsion device for a ship.

Background Art

A ship propulsion device is a device for providing power to a ship. Ship propulsors can be divided into two types, i.e., an active type and a reactive type, depending on how they function. The propulsors of ships with towlines or sails (for example, sailing boats) which are driven by manpower or wind power are of the active type. The propulsors of ships with paddles, oars, paddle wheels, hydraulic jet propulsors, screw propellers, etc. are of the reactive type. Modern transport ships mostly utilize reactive propulsors, and the most widely used is the screw propeller type. As the electric motor for driving the screw propeller generates a large amount of heat during operation, an important way to carry away the heat is to transfer the heat through the stator to the housing of the propulsion device which is exposed to seawater. In an electric motor, the rotor, the stator and the terminals of a stator coil are the main components that generate heat. However, in the past, a fully covered pod would have a large area that could not be cooled, resulting in local high temperatures. In order to solve the problem of heat dissipation, it is necessary to add a complicated air circulation cooling device to a hanger part of the pod. In order to arrange an air passage between the hanger and the housing of the electric motor, an extremely complicated connection structure is often required. Summary of the Invention

In order to solve one or more of the above problems, the present invention firstly proposes an electric motor including: a stator; a rotor which is rotatably provided on a motor shaft; and a housing structure which comprises a housing extending in an axial direction of the electric motor and surrounding the stator of the electric motor, and at least one heat dissipation strip which is provided and attached between an inner side surface of the housing facing the stator and an outer surface of the stator of the electric motor. The heat dissipation strips between the housing and the stator can facilitate heat conduction from the stator and the rotor to the surface of the housing, so that heat can be carried away by air, or by water under the application condition of the present invention.

According to an advantageous embodiment, the at least one heat dissipation strip extends in the axial direction of the electric motor.

According to a more advantageous embodiment, at least two heat dissipation strips are provided at regular intervals in a circumferential direction of the housing, with a gap formed between every two adjacent heat dissipation strips. With such an arrangement, uniform heat dissipation can be achieved all around the stator, and in addition, the reserved axial gap can make a space for air flow in the housing, thereby achieving heat dissipation in a more favorable manner.

According to an advantageous embodiment, the ratio of the length of the heat dissipating strip in the circumferential direction of the housing to the length of the gap in the circumferential direction of the housing ranges from 0.5 to 2. More preferably, the ratio ranges from 1 to 1.5. The specific value of the ratio may be calculated rationally based on the size and power of the electric motor.

According to an advantageous embodiment, the length of the heat dissipation strip is the same as the length of the stator of the electric motor in the axial direction of the electric motor. As a result, heat dissipation can be realized over the entire axial length of the stator.

According to an advantageous embodiment, the heat dissipation strip is made of a material with good heat conductivity, in particular of copper or an alloy of aluminum. The metal material may achieve better heat conduction.

According to an advantageous embodiment, an enhanced heat exchanging structure, in particular a rib, is provided in the gap of the propulsor housing. Thus, further heat dissipation can be achieved.

According to an advantageous embodiment, the cross section of the housing is circular, wherein the heat dissipation strip can be clamped in an annular void between the inner side surface of the housing and the outer surface of the stator.

According to an advantageous embodiment, an air cooling device is provided inside the housing structure of the electric motor. The air cooling device can achieve active heat dissipation, that is, further enhance heat dissipation by utilizing the air flow inside the electric motor.

According to an advantageous embodiment, the air cooling device is a fan provided on the motor shaft, or small fans which are powered by an external power supply and arranged to surround the motor shaft. The number of the externally powered small fans can be 1 to 8.

The present invention also provides a ship propulsion device correspondingly, an electric unit of the ship propulsion device comprising an electric motor of any one of the above embodiments . Brief Description of the Drawings

The following drawings are only intended to schematically illustrate and explain the present invention, and do not limit the scope of the present invention. In the drawings,

Fig. 1 schematically shows a podded propulsion device according to the prior art; Fig. 2 schematically shows a podded propulsion device according to an embodiment of the present invention;

Fig. 3 schematically shows a schematic diagram of a cross- section view taken along III-III of an electric unit of the podded propulsion device according to an embodiment of the present invention;

Fig. 4 schematically shows a schematic diagram of the interior of a podded propulsion device according to an embodiment of the invention;

Fig. 5 schematically shows a schematic diagram of the interior of a podded propulsion device according to another embodiment of the present invention; and

Fig. 6 schematically shows a schematic diagram of the interior of a podded propulsion device according to yet another embodiment of the present invention.

Detailed Description of Embodiments

In order to more clearly understand the technical features, objectives and effects of the present invention, particular embodiments of the present invention will be described with reference to the accompanying drawings.

Fig. 1 schematically shows a podded propulsion device according to the prior art. The propulsion device mounted on a lower part of a hull comprises an electric motor unit 1 with a housing structure. The electric motor unit 1 is mounted on a hanger 3 which is rotatably connected to the bottom of the hull through an engagement ring 4. A screw propulsor 5 or screw propeller 5 is mounted on the upstream end 2 of the electric motor unit 1. At the downstream end corresponding to the upstream end 2, the electric motor unit is connected to the hanger 3 via what is called a lower part 6. The lower part 6 is provided with a mounting hole 8 for fastening a bolt. The water flowing into the interior of the lower part 6 toward the electric motor unit 1 cools the electric motor unit.

In the embodiment shown according to the prior art, the hanger 3 and the electric motor unit 1 form an L-shaped structure, such that the outer wall of the electric motor unit 1 can be exposed to water to a greater extent, facilitating heat dissipation. However, the L-shaped structure makes the connection structure between the electric motor unit 1 and the arm member 3 less rigid than a fully covered type hanger arm. Its large cantilever structure also results in larger moments at the bend and requires thicker design.

Although not shown, in another podded propulsion device according to the prior art, the lower end of the hanger of the propulsion device extends in a longitudinal direction of the electric motor unit 1 and is connected thereto, thereby providing a robust connection between the hanger arm and the electric motor unit. Through this connection, the problems of stress and water flow regulation can be solved. However, due to this "fully covered" type of connection, the outer wall of the electric motor unit cannot be completely exposed to water to be sufficiently cooled. In the prior art, a special water cooling system is designed in the hanger. This inevitably further increases manufacturing difficulty and costs.

In order to make the electric motor unit have a good heat dissipation effect, the present invention proposes a specific solution .

Fig. 2 schematically shows an embodiment of a ship propulsion device 100 according to the invention.

The ship propulsion device 100 is, in particular, a podded ship propulsion device, which can be typically connected to a ship, especially to the bottom of a ship, via a slewing bearing plate 30 or an engagement ring and other components known in the art, such that the podded ship propulsion device 100 can be rotated so as to adjust the navigation direction of the ship. The ship propulsion device 100 shown in Fig. 2 comprises an electric unit 40. The electric unit 40 mainly comprises an electric motor 47 (not shown in Fig. 2; see Fig. 4) . The electric motor comprises a housing 44, and a stator, a rotor, a motor shaft, etc. of the electric motor enclosed therein by the housing 44. The structure of the electric motor is known in the prior art and will not be described in detail herein. A propulsor 60 is provided at one end 42 of the electric unit 40, and is typically a screw propulsor or screw propeller 60. In the embodiment shown in Fig. 2, the screw propeller 60 comprises four specially designed blades 62. It is conceivable that the number of blades can also be 3 or 5, and the shape of the blades also needs to be designed according to actual thrust and so on. In the present invention, the area at the end of the electric unit 40 close to the screw propeller 60 can be referred to as a proximal area 42. It is not limited to the point closest to the screw propeller 60, but may indicate an area closer to the screw propeller 60 compared to the other end of the electric unit 40, in particular on its housing 44. Corresponding to this, the area on the electric unit 40, in particular the area on the housing 44 that is closer to the other end or away from the screw propeller 60 is called a distal area 41.

The ship propulsion device 100 further comprises a hanger structure 50 that connects the electric unit 40 with the slewing bearing plate 30. The hanger structure shown in Fig. 2 forms an approximately triangular shape seen from the perspective of the drawing. Its bearing end 56 close to the slewing bearing plate 30 has a smaller cross section which can be engaged with the slewing bearing plate 30. A body 55 of the hanger structure 50 extends from the bearing end 56 toward the electric unit 40. The body 55 is surrounded by a hanger shell 54 to form a hollow structure. The hanger shell 54 is configured to enable the cross section of the hanger structure 50 in the direction of water flow to be streamlined. The hanger shell 54 forms two legs at an end away from the bearing end 56, among which a first leg 51 is connected to the housing 44 of the electric unit 40 at the distal area 41 away from the screw propeller in the axial direction, and a second leg 52 is used for connecting with the housing 44 of the electric unit 40 at the proximal area 42 close to the screw propeller in the axial direction. As the first leg 51 and the second leg 52 are spaced apart from each other, a void 53 is formed between the first leg and the second leg. As the void 53 per se is also formed by the hanger shell 54, and is similar to a "bridge" spanning between the first leg and the second leg, such that at least part of the housing 44 between the proximal area 42 and the distal area 41 of the housing 44 of the electric motor unit 40 is not covered by the hanger shell of the hanger structure 50. As a result, the hanger structure of such a "two-end suspension type" structure can not only maintain the firmness of the covered type hanger, that is, it is possible to maintain the strength thereof without requiring a heavy structure, but can also expose a large area of the housing 44 of the electric unit to water so as to achieve sufficient heat dissipation. Therefore, the integration of the advantages of the "L" shaped cantilever structure and the fully covered hanger structure is achieved through the structural improvement.

Although not shown in Fig. 2, it is conceivable that the interior of the housing 44 of the electric motor unit 40 is also hollow. Also notably, the interior of the first leg 51 and the second leg 52 formed by the hanger shell 54 may be hollow as well, and thus the inner cavity of the hanger structure 50 is allowed to be in communication with the inner space of the electric unit 40. It should be noted that the ends of the first leg 51 and the second leg 52 may be open ends (i.e., the hanger shell 54 is not sealed and is open at the ends of the first leg 51 and the second leg 52, and thus the inner cavity of the hanger shell 54 can communicate with the inner cavity of the housing 44 of the electric unit through the first leg and the second leg) . Alternatively, when the ends of the first leg 51 and the second leg 52 are closed, the housing 44 not covered by the hanger structure can be used for heat dissipation or a fan can be used for heat dissipation. Of course, one of the first leg 51 and the second leg 52 may be closed, and the other one may be open.

Fig. 3 shows a schematic diagram of a cross section view taken along III-III in Fig. 2. In the present invention, the heat dissipation performance of the electric unit 40 of the ship propulsion device is further optimized by a new design of the housing structure of the electric motor 47. As shown, the electric motor 47 comprises a rotor 471 that is rotatably supported on a motor shaft 470. The rotor 471 is surrounded by a stator 473 of the electric motor on its circumferential outer side. The structure of the electric motor is known in the art and will not be described in detail herein.

The housing 44 is a housing 44 that extends in the axial direction of the electric motor, and the electric motor 47 is surrounded by the housing 44. The housing 44 is typically a cylindrical shape extending in the direction of the axis x of the electric motor, but may also have, for example, a rectangular, in particular square, cross-section (not shown) . In a preferred embodiment, the cross section taken along III- III is circular in shape, thereby forming an annular first annular void 448 between the housing 44 and the stator 473 of the electric motor. In an embodiment in accordance with the present invention, at least one heat dissipation strip 441 is provided between an inner side 445 of the housing 44 facing the stator of the electric motor and an outer surface 446 of the stator 473. These heat dissipation strips 441 are preferably clamped between the housing 44 and the stator 473. In the embodiment shown in Fig. 3, a plurality of heat dissipation strips 441 are provided as an example. The length of the heat dissipation strips 441 is the same as the length of the stator 473, but may also be less than the length of the stator. These heat dissipation strips 441 are preferably arranged in parallel at regular intervals in a lengthwise direction of the housing 44. In particular, these heat dissipation strips 441 are configured to have the same size (to have the same cross- sectional area and shape) . Thus, the gaps 442 between every two adjacent heat dissipation strips 441 also have approximately the same width. The heat dissipation strips 441 are made of a metal with good heat conductivity, such as copper or aluminum alloy. In the illustrated embodiment, the heat dissipation strips are copper strips having a height of 2 cm and a width of about 3 cm, and the spacing between each two copper strips 441 is 1 cm to 3 cm, thereby forming a series of axial ventilation channels. The heat dissipation strips 441 are pressed tightly between the inner side surface 445 of the housing 44 and the outer surface 446 of the stator 473, and thus a part of the heat from the stator can be conducted directly to the housing 44 by the heat dissipation strips 441 for conducting heat, and the heat can be conducted to water by means of the housing 44. Also notably, air may also pass through the gap between the rotor 471 and the permanent magnet and the gap between the rotor 471 and the stator 473 and then through the voids in the terminals to dissipate heat, and through the gap 442 between the housing 44 and the stator 473 to conduct heat to the housing and finally to water.

Fig. 3 shows a preferred embodiment of the present invention. In practice, a smaller number of heat dissipation strips can be selected, and the width and height of the heat dissipation strips can also be configured according to actual situations. For example, in the illustrated embodiment, the ratio of the length of the heat dissipating strips 441 in the circumferential direction of the housing 44 to the length of the gap in the circumferential direction of the housing 44 is 1 : 1 or 3 : 2. In addition, the optimal ratio relationship can be determined through flow field and temperature field calculation according to the size of the electric motor, heat dissipation amount of each component, wind pressure of the fan, component materials, etc. When the cross section of the housing 44 is not circular but rectangular, the heat dissipation strips disposed in different positions may be designed in different shapes so that at least a part of the area of the heat dissipation strips can make contact with both the inner side surface 445 of the housing and the outer surface 446 of the stator at the same time. It should be pointed out that the heat dissipation strip 441 may be a separate component clamped between the inner side surface 445 of the housing 44 and the outer surface 446 of the stator 473 by means of a clamping force. In addition, the heat dissipation strips 441 may also be ribs integrally formed with the housing 44 or the outer surface 446 of the stator.

In addition, as the heat dissipation strip 441 is clamped between the housing 44 and the stator 473, the width of the heat dissipation strip 441 can be designed to be larger when the number of the heat dissipation strips 441 is small. In addition, in order to further adhere to the housing 44 and the stator 473, the heat dissipation strip 441 can also be designed to be sector-shaped. As a result, the arc-shaped side surface can better conform to the inner circumferential surface of the housing 44 and the outer surface of the stator 473.

Fig. 4 exemplarily shows a schematic diagram of the air flow inside the electric motor 47 according to an embodiment of the present invention. In this embodiment, the ends of the first leg 51 and the second leg 52 of the hanger structure 50 are closed. That is, the inner cavity of the hanger structure 50 and the interior of the housing 44 of the electric motor 47 are not in communication with each other. Therefore, in order to achieve better heat dissipation, further heat dissipation can be achieved by installing a fan 49 on the motor shaft, in addition to exposing the housing 44 of the electric unit to water by a large area. As indicated by arrow 70, the fan 49 forces air to flow in the gap 442 between the inner side surface 445 of the housing 44 of the electric motor and the outer surface of the stator 473. Also notably, air may also pass through the gap between the rotor 471 and the permanent magnet and the second annular void 449 between the rotor 471 and the stator 473, and then through the voids in the terminals to dissipate heat, and through the gap 442 between the housing 44 and the stator 473 to conduct heat to the housing and finally to water. Of course, a large part of the heat can be directly conducted to water through the stator 473, the heat dissipation strip 441, and the housing 44 by providing the heat dissipation strip 441. As a result, the electric unit can have very good heat dissipation performance.

Referring to Fig. 5, a schematic diagram of the air flow inside the electric motor 47 according to yet another embodiment of the present invention is schematically shown. In the embodiment illustrated in Fig. 5, the ends of the first leg 51 and the second leg 52 of the hanger structure are open ends (i.e., the hanger shell 54 is not sealed and is open at the ends of the first leg 51 and the second leg 52), and thus the inner cavity of the hanger shell 54 can communicate with the inner cavity of the housing 44 of the electric unit through the first leg and the second leg. In this embodiment, the fan 49 forces air to circulate in the inner cavity of the housing 44 and the hanger shell 54. As indicated by arrow 70, the fan 49 forces air to flow between the inner side surface 445 of the housing 44 and the outer surface of the stator 473. Also notably, air may also pass through the gap between the rotor 471 and the permanent magnet and the second annular void 449 between the rotor 471 and the stator 473, and then through the voids in the terminals to dissipate heat, and through the gap 442 between the housing 44 and the stator 473 to conduct heat to the housing and finally to water. In the embodiment in which the hanger shell 54 is in communication with the housing 44, further heat dissipation can be achieved by the hanger shell 54. Therefore, the hot air between the stator and the rotor of the electric motor 42 is driven into the inner cavity of the hanger shell 54. As the inner cavity of the hanger shell 54 per se has no heat generating components, and its outer surface is in contact with water by a large area, the temperature of the circulating air can be lowered more quickly, and the cooled air may enter and cool the electric motor. Of course, air can also be circulated in a direction opposite to the direction indicated by arrow 70 by installing different sector-shaped fans .

It is conceivable that in order to further improve the cooling effect, a speed increaser (gear) may be installed inside the housing 44, so that the fan 49 is driven by the motor shaft via the speed increaser, thereby further increasing the rotation speed of the fan 49 to achieve a better active heat dissipation effect. The speed increaser may be arranged coaxially with the motor shaft, which will not be described in detail herein.

Fig. 6 shows yet another embodiment according to the present invention. In this embodiment, the active cooling device can be a plurality of small fans 49' distributed inside the housing 44. For example, there may be 3 to 9 small fans 49' arranged evenly along the circumference of the housing 44. These small fans are powered by an external power line to achieve uniform air supply.

It can be understood that the construction of the electric motor according to the present invention can be applied not only to the ship propulsion device, but also to any electric motor which has a higher demand on heat dissipation, especially to an electric motor with a higher power.

It should be understood that although this specification describes the present invention according to each embodiment, it does not mean that each embodiment only comprises one independent technical solution, and such a description manner of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, where technical solutions in the embodiments may also be combined appropriately to form other implementations which can be understood by those skilled in the art.

The above is merely exemplary particular embodiments of the present invention and is not intended to limit the scope of the present invention. Any equivalent change, modification and combination made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the protection scope of the present invention. List of reference numerals

1 electric motor unit

3 hanger

4 engagement ring

5 screw propeller

6 lower part

8 mounting hole

30 slewing bearing plate

40 electric unit

41 distal end

42 proximal end

44 housing

45 first connection area

46 second connection area

47 electric motor

48 bearing

49 cooling device; fan

49' cooling device; small fan

50 hanger structure

51 first leg

51 second leg

53 void

54 hanger shell

55 body of hanger structure

56 bearing end of hanger structure

60 screw propeller; propulsor

62 blade

70 air circulation path

100 ship propulsion device

441 heat dissipation strip

442 gap

445 inner side surface

446 outer surface of stator

448 first annular void

449 second annular void motor shaft rotor stator

Claims

1. An electric motor (47), comprising:

a stator (473) ;

a rotor (471) which is rotatably provided on a motor shaft (470); and

a housing structure which comprises:

a housing (44) extending in an axial direction of the electric motor (47), the housing (44) surrounding the stator (473) of the electric motor; and

at least one heat dissipation strip (441) which is provided and attached between an inner side surface (445) of the housing (44) facing the stator (473) and an outer surface of the stator (473) of the electric motor.

2. The electric motor of claim 1, wherein the at least one heat dissipation strip (441) extends in the axial direction of the electric motor (47) .

3. The electric motor of claim 2, wherein at least two heat dissipation strips (441) are provided at regular intervals in a circumferential direction of the housing (44), with a gap (442) formed between every two adjacent heat dissipation strips (441) .

4. The electric motor of claim 3, wherein the ratio of the length of the heat dissipating strip (441) in the circumferential direction of the housing (44) to the length of the gap in the circumferential direction of the housing (44) ranges from 0.5 to 2.

5. The electric motor of any one of claims 1 to 4, wherein the length of the heat dissipation strip (441) is the same as the length of the stator (473) of the electric motor (47) in the axial direction of the electric motor.

6. The electric motor of any one of claims 1 to 5, wherein the heat dissipation strip (441) is made of a material with good heat conductivity, in particular of copper or an alloy of aluminum.

7. The electric motor of any one of claims 1 to 6, wherein an enhanced heat exchanging structure, in particular a rib, is provided in the gap (442) of the propulsor housing (44) .

8. The electric motor of any one of claims 1 to 7, wherein the cross section of the housing (44) is circular, and wherein the heat dissipation strip (441) can be clamped in an annular void (444) between the inner side surface (445) of the housing (44) and the outer surface of the stator (473) .

9. The electric motor of any one of claims 1 to 8, wherein an air cooling device (49; 49') is provided inside the housing structure of the electric motor.

10. The electric motor of claim 9, wherein the air cooling device (49; 49' ) is a fan (49) provided on the motor shaft (470), or small fans (49') which are powered by an external power supply and arranged to surround the motor shaft (470) .

11. A ship propulsion device, wherein an electric unit of the ship propulsion device comprises an electric motor of any one of claims 1 to 9.