EP3922040A1

EP3922040A1 - System for cooling the stationary winding of an induction motor

Info

Publication number: EP3922040A1
Application number: EP20710586.7A
Authority: EP
Inventors: Hector QUERRY; Guillaume Heisel; Adrien HOFFET; Jean-Luc Thuliez; Etienne Crozier; Robin ZIMMERMANN
Original assignee: Oltramare Michel
Current assignee: Oltramare Michel
Priority date: 2019-02-06
Filing date: 2020-02-06
Publication date: 2021-12-15
Also published as: BR112021014602A2; CA3127120A1; JP2022519475A; US11930340B2; WO2020161669A1; US20220141591A1

Abstract

The present invention relates to principles for cooling the stationary winding (4) of an induction motor (1), said winding (4) being positioned outside the movable armature (7). The cooling can be achieved by means of cooling fins (2a), openings (2b and 2c) allowing the ventilation of the winding (4) with or without a fan (12), a fluid circuit (13) outside the bowl (3), a fluid circuit (15) inside the bowl (3), a fluid circuit inside the winding (4), and/or the addition of heat pipes (18) inside the bowl (3). This motor as presented can be used, without limitation, inside loudspeakers or vibrators.

Description

COOLING SYSTEM OF THE FIXED COIL OF AN INDUCTIVE MOTOR

Corresponding request

The present application claims the priority of the earlier Swiss application N ° CH 00136/19 filed on February 6, 2019 in the name of Mr. Michel OLTRAMARE, the content of this earlier application being incorporated by reference in its entirety in the present application.

Technical area

The present invention relates to the means for cooling the fixed coil of an inductive motor.

The present invention finds for example an application in the field of actuators in general, and more particularly for loudspeakers and vibrating pots used for fatigue tests. These applications are of course not limiting and other applications are possible in the context of the present invention by making use of the principles described in the present application.

Prior art

Many patents deal with the production of inductive motors with a fixed coil: US2621261 A, US4965839A, US5062140A, US5742696A, US6359996B1, US6542617B1 or even US8009857B2. These patents highlight the magnetic, electrical, mechanical or acoustic properties of this type of configuration. However, few solutions are proposed to solve the coil cooling problem. On inductive motors, however, this is a major operating limit. In fact, the current flowing in the coil causes it to heat up and then, by conduction and radiation, to heat all the parts of the engine. The increase in temperature causes a modification of the impedance, and therefore a disturbance of the current, the latter being determined by the impedance. This results in a variation of all the characteristics of the motor, in particular the magnetic field generated by the coil and the force developed by the moving armature. In the case of a loudspeaker, the increase in the temperature of the membrane connected to the armature leads to a variation in its modulus of elasticity. This will therefore vibrate differently depending on its level of heating. Thus, all the performances of the inductive motor vary simultaneously under the effect of temperature, making it difficult to control. In the case of an embodiment in the form of a loudspeaker, these elements therefore have a fundamental importance and influence for the quality of the vibratory reproduction of the motor and of the sound of the loudspeaker.

On the most commonly used loudspeaker motors, the coil, commonly referred to as a "voicecoil", is movable and fixed to the membrane. This mobility creates a relative movement between the coil and the air which surrounds it, achieving a summary natural cooling. However, it prevents any truly effective cooling. Some patents nevertheless offer certain solutions GB1348535A, JPH03239099A, JPS5586288A,

JPS56161798A, JPS59216394A. However, these solutions have an impact on the efficiency of the motor, the liquids in contact with the coil slowing its movement.

In events, to overcome the drawbacks linked to the increase in temperature as described above, the speaker columns containing the loudspeakers are frequently doubled, one column operating while its twin is stopped. The operator thus switches from one column to another when the temperature of the loudspeakers of one of the columns reaches an operating level for which the sound quality is too affected. The number of speaker columns to be transported and installed is thus doubled, which increases the investment in sound equipment, and the bill for the event organizer.

Finally, heating problems are constraining for the choice of the material of the magnets: beyond a certain temperature, the magnets demagnetize and become unusable. They therefore have a maximum operating temperature which must be respected. Overall, the more a material has strong magnetization, the lower its operating temperature. As current inductive motors heat up strongly, the materials used to make the magnets are not the most optimum in terms of magnetism.

Disclosure of the invention

The present invention overcomes all of the drawbacks mentioned above and in particular proposes to cool the fixed coil of an inductive motor. The application presented below is that of an actuator motorizing a loudspeaker, but the invention can be used for all electromagnetic actuators, such as for example vibrating pots, and other applications.

In one embodiment, the engine, as defined in the preamble of the claims, is characterized in that it has a fixed coil positioned outside the cylinder formed by the armature, and means for cooling it. These means described below can be applied separately or combined with each other in different illustrative and non-limiting embodiments.

In embodiments, the motor magnets are formed from a material of high energy density and low operating temperature. For example, these materials are alloys of neodymium, iron and boron Nd2Fei4B such as N48H, or N50M or other equivalent and suitable materials. According to embodiments, an external bowl, in which the coil is placed, is provided with a plurality of fins, increasing the contact surfaces with the external environment. The fins can be formed directly on the bowl or added. They can be made of steel, stainless steel, aluminum or any other material having good thermal conductivity.

According to embodiments, the motor can be configured to allow an air knife to exhaust hot air around the coil in order to cool it with cooler air coming from the outside.

According to embodiments, the motor can include openings between the magnetic air space and the external environment, allowing an air flow generated by the chimney effect to cool the coil.

According to embodiments, the motor can include a fan and one or more openings between the magnetic air space and the external environment, creating an air circulation around the coil and a decrease in temperature in the air space. magnetic air, the air coming from outside and following the geometries of the coil by the Coandâ effect, increasing heat exchange.

According to embodiments, the motor can include openings with variable sections between the external environment, the magnetic air space and / or the fan, in order to obtain more efficient cooling of the air circulating around the coil. .

According to embodiments, the motor comprises a fluidic cooling circuit on the outer faces of the outer bowl.

According to some embodiments, the circuit in which a heat transfer fluid circulates is made around the outer bowl in order to cool the latter and therefore the coil. According to embodiments, a heat transfer fluid is placed directly around the coil for direct cooling.

According to embodiments, the coil is formed by winding a tube of small diameter. A heat transfer fluid circulating inside this tube cools it.

According to embodiments, heat pipes are mounted in the outer bowl in order to amplify the heat exchanges between the hot coil inside and the cold outside environment.

Efficient motor cooling allows the use of more powerful permanent magnets, resulting in a more efficient motor.

According to embodiments, the invention relates to a device or an object comprising at least one inductive motor as described in the present application.

According to some embodiments, the motor is a loudspeaker or a vibrating pot for example.

According to some embodiments, the motor comprises openings between the space under the membrane, the magnetic air space and the external environment, allowing the air flow generated by the oscillating membrane to cool the coil.

According to embodiments, the engine comprises one or more valves between the external environment and the space under the membrane, so as to introduce fresh air coming from the external environment. These and other embodiments are now described with reference to the figures.

Brief description of the drawings

The present invention and its advantages will appear better in the description of several embodiments given by way of nonlimiting examples, with reference to the appended drawings in which:

- Figure 1a shows a sectional view of the engine equipped with axial cooling fins according to one embodiment of the invention,

- Figure 1b shows a sectional view of the engine equipped with radial cooling fins according to one embodiment of the invention,

- Figure 2a shows a sectional view of the engine configured to cool by the chimney effect according to one embodiment of the invention,

- Figure 2b shows a sectional view of the engine configured to receive a blade of cooling air from the coil, the air being created by the movement of the membrane according to one embodiment of the invention,

- Figure 2c shows a sectional view of the engine configured to receive a blade of cooling air from the coil, the air being created by the movement of the membrane, and a valve for introducing cold air coming from from the outside according to one embodiment of the invention,

- Figure 2d shows a sectional view of the engine configured to receive a blade of cooling air from the coil, under the suction of a fan according to one embodiment of the invention, FIG. 3 represents a sectional view of the engine equipped with external cooling by heat transfer fluid according to one embodiment of the invention,

- Figure 4 shows a sectional view of the engine equipped with cooling by heat transfer fluid, directly in contact with the coil according to one embodiment of the invention,

- Figures 5a and 5b show a sectional view of the engine equipped with a coil inside which circulates a coolant according to one embodiment of the invention,

- Figure 6 shows a sectional view of the engine equipped with cooling heat pipes according to one embodiment of the invention.

Detailed description of the invention and embodiments

With reference to the embodiments illustrated in the figures, the loudspeaker inductive motor 1 comprises a bowl 2 and a core 3 both made of a magnetically conductive material, preferably steel for example; a coil 4 mounted inside said bowl 2 and supplied with an alternating current; of one or more magnets 5 charged radially and mounted outside said core 3, so as to form with said coil 4 a magnetic air space 6; an armature 7 made of a conductive material, preferably aluminum for example, mounted in said magnetic air space 6, and connected to a speaker membrane 9. Said membrane 9 is fixed to basket 11. During operation of the loudspeaker, said coil 4 generates heat. This heat is transmitted to said magnetic air space 6 surrounding said coil 4, and to said bowl 2 in contact with or near said coil 4. With reference to the embodiment illustrated in Figures 1a and 1b, the bowl 2 is provided with fins 2a on its outer faces. In Figure 1a, the cooling fins are oriented axially with respect to the cylinder. In Figure 1b, the cooling fins are oriented radially with respect to the cylinder. Said fins 2a make it possible to increase the heat exchange surfaces between said bowl 2 and the external environment 8. With this large exchange surface, the calories present in the form of heat in said bowl 2 are evacuated more efficiently, realizing cooling of said bowl 2, and consequently of said magnetic air space 6 and coil 4. The number of fins 2a is not limited to that illustrated in the figures but may be different. The fins 2a may or may not be distributed evenly. They may or may not have the same shape and / or size. All of these parameters (and more) can be adapted depending on the circumstances, bowl size and / or application.

Favorably a fan-type element, not shown in Figures 1a and 1b, can be added to the outside of said inductive motor 1 in order to create a radial air flow around said fins 2a to always have air. cold air around said fins 2a, so as to increase heat exchange and improve the cooling of said bowl 2, magnetic air space 6 and coil 4.

With reference to the embodiment illustrated in FIG. 2a, the bowl 2 comprises upper ducts 2b between said external medium 8 and said magnetic air space 6, as well as lower ducts 2c between said magnetic air space 10 and said external medium 8. Said ducts 2b and 2c are positioned directly in front of said coil 4, oriented in the same direction as that of the axis of said coil 4. In this way, when said coil 4 heats the air contained in said magnetic air space 6, a chimney effect occurs, the hot air of lower density rising, replaced in said magnetic air space 6 by cool air coming from below from said external environment 8. With reference to the embodiment illustrated in Figures 2b and 2c, the bowl 2 comprises upper ducts 2b between the space under membrane 10 and said magnetic air space 6, as well as lower ducts 2c between said space of magnetic air 10 and said external medium 8. Said conduits 2b and 2c are positioned directly in front of said coil 4, oriented in the same direction as that of the axis of said coil 4. In FIG. 2a, when the loudspeaker is in operation, said membrane 7 vibrates, which alternately creates overpressures and depressions in said space under membrane 10, under said membrane 7. These pressures and depressions create an axial air movement passing through said upper and lower ducts 2b 2c, thus expelling the hot air present around said coil 4 in order to replace it with colder air coming from said space under the membrane 10 or from said external medium 8. According to FIG. 2c, valves 11 a mounted on the other. or said space under membrane 10 can make it possible to supply cold air to said space under membrane 10.

With reference to the embodiment illustrated in FIG. 2d, a fan 12 is placed so as to generate an air flow directed in a direction substantially parallel to the axis of said bowl 2. Openings 11 b allow said to communicate. membrane space 10 with the external environment 8. The fan 12 in operation draws hot air around said coil 4, through said lower ducts 2c, creating a vacuum in said magnetic air space 10. Due to this vacuum , fresh air coming from said external medium 8 is sucked through said openings 11b and said upper ducts 2b to be placed around said coil 4, thus allowing it to be cooled. The Coandâ effect finally makes it possible to improve this cooling, the air flow sticking to the geometries of said coil 4. Advantageously but not exclusively, said upper ducts 2b and lower ducts 2c have side walls inclined relative to the direction. of air flow, so as to have variable sections. This variation in section creates areas of pressure and depression. Air relaxation after passage in said upper duct 2b thus allows cooling of the air entering said magnetic air space 10, and therefore better cooling of said coil 4.

With reference to the embodiment illustrated in FIG. 3, said bowl 2 is surrounded by a fluidic circuit 13. In said fluidic circuit 13, a heat transfer fluid circulates, favorably pure water or a dielectric liquid of the “3M Novec” type. specially designed for cooling electronic components by immersion. Said heat transfer fluid makes it possible to evacuate the calories present in the form of heat in said bowl 2, cooling said bowl 2, and consequently of said magnetic air space 6 and coil 4. Favorably, said fluid circuit is connected to a pumping system and a cooling system, not shown in FIG. 3, so as to ensure circulation of said cold heat transfer fluid in said fluid circuit 13, for better cooling of said bowl 2, magnetic air space 6 and coil 4.

With reference to the embodiment illustrated in FIG. 4, said bowl 2 comprises a fluidic circuit 15 on its inner face, in contact with said coil 4. In said fluidic circuit 15 circulates a heat transfer fluid, favorably pure water or a dielectric liquid type "3M Novec" specially designed for cooling electronic components by immersion. Said heat transfer fluid makes it possible to evacuate the calories present in the form of heat in said coil 4, effecting direct cooling thereof. Favorably, said fluidic circuit 15 is connected to a pumping system and to a cooling system, not shown in the figure, so as to ensure circulation of said cold heat transfer fluid in said fluidic circuit 15, for better cooling of said fluid. coil 4.

With reference to the embodiment illustrated in FIGS. 5a and 5b, said coil 4 is produced by winding an electrically conductive tube. A heat transfer fluid circulates inside this tube, favorably pure water or a dielectric liquid type "3M Novec" specially designed for cooling electronic components by immersion. Said heat transfer fluid makes it possible to evacuate the calories present in the form of heat in said coil 4, providing direct cooling from the inside thereof. Favorably, said coil 4 is connected to a pumping system and to a cooling system, not shown in the figure, so as to ensure a circulation of said cold coolant in said coil 4, for better cooling thereof. .

With reference to the embodiment illustrated in FIG. 6, said bowl 2 is provided with one or more heat pipes 18 over its entire periphery. In a nonlimiting manner, these heat pipes may be of cylindrical shape and mounted in cavities hollowed out substantially radially in said bowl 2. In this configuration, they connect the outer part of said inductive motor 1 to the inner part of said inductive motor 1, occupied by said coil 4 and by said magnetic air space 6. Said heat pipes 18 allow a greater heat exchange density than the material constituting said bowl 2. In the case of air cooling as shown in figure 1, or a fluidic cooling as shown in Figure 3, said heat pipes make the cooling of said coil 4 and said magnetic air space 6 more efficient, since they allow to evacuate a greater number of calories to the 'outside.

Said cooling elements make it possible to decrease the temperature inside said inductive motor 1. Thus, materials having better energy densities but lower operating temperatures can be used to constitute said magnets 5, and therefore improve the efficiency of said motor. inductive 1.

This invention can be adapted to applications other than that of the loudspeaker, particularly in those applications where one must generate large and precise vibrations over a large period of time. It's the case for example for vibrating pots. The principle of the invention is thus not limited to the embodiments and embodiments described, but is liable to be modified within the framework of the protection sought. The embodiments described are by way of illustrative examples and should not be considered as limiting. Other embodiments may use means equivalent to those described for example. The embodiments can also be combined with each other depending on the circumstances, or means used in one mode can be used in another mode.

Claims

1. Inductive motor comprising at least one magnet (5), a bowl (2) with a fixed coil (4) outside a moving armature (7), comprising means for cooling the fixed coil, placed at the outside of the armature.

2. Inductive motor according to claim 1, having magnets (5) comprising a material with high energy density and low operating temperature.

3. Inductive motor according to one of claims 1 or 2, comprising cooling fins (2a) present on the periphery of the outer bowl (2).

4. Inductive motor according to one of the preceding claims, comprising openings (2b, 2c) between the magnetic air space (10) and the external environment (8), allowing an air flow generated by the chimney effect. to cool the coil.

5. Inductive motor according to one of the preceding claims, comprising a fan (12) and at least one opening (11 b) between the magnetic air space and the external environment, creating air circulation around the coil. and a decrease in temperature in the magnetic air space, the air coming from outside and depending on the geometries of the coil by the Coandâ effect, increasing heat exchange.

6. Inductive motor according to claim 5, comprising openings with variable sections between the external environment, the magnetic air space and / or the fan, in order to obtain more efficient cooling of the air circulating around the coil. .

7. Inductive motor according to one of the preceding claims, comprising a fluid circuit (15) for cooling on the outer faces of the outer bowl.

8. Inductive motor according to one of the preceding claims, comprising a fluidic cooling circuit on the inner faces of the outer bowl, in contact with the coil.

9. Inductive motor according to one of the preceding claims, comprising a coil produced by means of a hollow tube inside which circulates a cooling fluid.

10. Inductive motor according to one of the preceding claims, comprising one or more heat pipes (18) positioned substantially radially in the outer bowl.

11. Device comprising at least one inductive motor according to one of the preceding claims.

12. Device according to the preceding claim, said device being a loudspeaker or a vibrating pot.

13. Loudspeaker according to claim 12, comprising openings (2b, 2c) between the space under the membrane (7), the magnetic air space (10) and the external environment (8), allowing the flow of air. air generated by the oscillating membrane (7) to cool the coil.

14. Loudspeaker according to claim 13, comprising one or more valves (11a) between the external environment and the space under the membrane so as to introduce fresh air from the external environment.