System for cooling the stationary winding of an induction motor

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

[0001] This application claims priority from the earlier Swiss application No. CH 00136 / 19 filed on February 6, 2019 in the name of Mr. Michel OLTRAMARE, the contents of this earlier application being incorporated by reference in its entirety into the present application. Technical field

[0002] The present invention relates to means for cooling the fixed coil of an inductive motor.

[0003] 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 within the framework of the present invention by using the principles described in the present application. Prior art

[0004] Many patents deal with the production of inductive motors with fixed coils: US2621261A, US4965839A, US5062140A, US5742696A, US6359996B1, US6542617B1 or even US2008199039A1 These patents highlight the magnetic, electrical, mechanical or acoustic properties of this type of configuration. However, few solutions are proposed to solve the problem of cooling the coil. On inductive motors, however, this is a major operating limitation.

[0005] Indeed, the current flowing in the coil causes it to heat up and then, by conduction and radiation, the heating of all the parts of the motor. The increase in temperature causes a change in the impedance, and therefore a disturbance in the current, the latter being determined by the impedance. This results in a variation in 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. It 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 a loudspeaker design, these elements therefore have a fundamental importance and influence on the quality of the vibration reproduction of the motor and the sound of the loudspeaker.

[0006] In the most commonly used loudspeaker motors, the coil, commonly called "voicecoil", is mobile and fixed on the membrane. This mobility creates a relative movement between the coil and the air surrounding it, achieving basic natural cooling. However, it prevents any truly effective cooling. Some patents nevertheless propose certain solutions: GB1348535A, JPH03239099A, JPS5586288A, JPS56161798A, JPS59216394A. These solutions, however, have an impact on the motor's efficiency, as liquids in contact with the coil slow down its movement.

[0007] In the event industry, to overcome the drawbacks of increasing temperature as described above, the speaker columns containing the loudspeakers are frequently doubled, with one column operating while its twin is switched off. The operator thus switches from one column to the other when the temperature of the loudspeakers in one of the columns reaches an operating level at which the sound quality is too affected. The number of speaker columns to be transported and implemented is thus doubled, which increases the investment in sound equipment, and the event organizer's bill.

[0008] Heating issues are finally a constraint when choosing magnet materials: beyond a certain temperature, magnets demagnetize and become unusable. They therefore have a maximum operating temperature that must be respected. Generally, the stronger a material's magnetization, the lower its operating temperature. Since current inductive motors heat up significantly, the materials used to make the magnets are not the most optimal in terms of magnetism. Statement of the invention

[0009] The subject matter of the protection sought is defined by claim 1.

[0010] In one embodiment, the motor, 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 set out below can be applied separately or combined with each other in different illustrative and non-limiting embodiments. In embodiments, the magnets of the motor are formed from a material with high energy density and low operating temperature. For example, these materials are alloys of neodymium, iron and boron Nd 2 Fe 14 B such as N48H, or N50M or other equivalent and suitable materials.

[0011] According to embodiments, an outer 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.

[0012] According to embodiments, the motor may be configured to allow an air blade to exhaust hot air around the coil to cool it with cooler air from outside.

[0013] According to embodiments, the motor may include openings between the magnetic air gap and the external environment, allowing a stack-generated airflow to cool the coil.

[0014] According to embodiments, the motor may include a fan and several openings between the magnetic air space and the external environment, creating an air circulation around the coil and a decrease in temperature in the magnetic air space, the air coming from the outside and following the geometries of the coil by Coand effect. , increasing heat exchange.

[0015] According to embodiments, the motor may include variable section openings between the external environment, the magnetic air gap and / or the fan, in order to obtain more efficient cooling of the air circulating around the coil.

[0016] According to embodiments, the engine comprises a cooling fluid circuit on the outer faces of the outer bowl.

[0017] According to embodiments, the circuit in which a heat transfer fluid circulates is produced around the outer bowl in order to cool it and therefore the coil.

[0018] In some embodiments, a heat transfer fluid is placed directly around the coil for direct cooling.

[0019] According to the invention, the coil is made up of a small diameter tube. A heat transfer fluid circulating inside this tube allows it to be cooled.

[0020] According to embodiments, heat pipes are mounted in the outer bowl in order to amplify the thermal exchanges between the hot coil inside and the cold external environment.

[0021] Efficient motor cooling allows the use of more powerful permanent magnets, resulting in a more efficient motor.

[0022] According to embodiments, the invention relates to a device or an object comprising at least one inductive motor as described in the present application.

[0023] According to embodiments, the motor is a loudspeaker or a vibrating pot for example.

[0024] According to embodiments the motor comprises openings between the sub-membrane space, the magnetic air space and the external environment, allowing the airflow generated by the oscillating membrane to cool the coil.

[0025] 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.

[0026] These and other embodiments are now described with reference to the figures. Summary description of the drawings

[0027] The present invention and its advantages will appear better in the description of several embodiments given as non-limiting examples, with reference to the appended drawings in which: there Figure 1a represents a sectional view of the engine equipped with axial cooling fins according to an embodiment which is not part of the invention Figure 1b represents a sectional view of the engine equipped with radial cooling fins according to an embodiment which is not part of the invention Figure 2a represents a sectional view of the engine configured to cool by chimney effect according to an embodiment which is not part of the invention. Figure 2b represents a sectional view of the motor configured to receive a blade of cooling air from the coil, the air being created by the movement of the membrane according to an embodiment which is not part of the invention Figure 2crepresents a sectional view of the motor configured to receive a blade of cooling air from the coil, the air being created by the movement of the membrane, and a valve allowing the introduction of cold air coming from the outside according to an embodiment which is not part of the invention, the figure 2d represents a sectional view of the motor configured to receive a blade of cooling air from the coil, under the suction of a fan according to an embodiment which is not part of the invention, the Figure 3 represents a sectional view of the engine equipped with external cooling by heat transfer fluid according to an embodiment which is not part of the invention, the Figure 4 represents a sectional view of the engine equipped with cooling by heat transfer fluid, directly in contact with the coil according to an embodiment which is not part of the invention, the Figures 5a And 5brepresent a sectional view of the engine equipped with a coil inside which a heat transfer fluid circulates according to an embodiment of the invention, the Figure 6 represents a sectional view of the engine equipped with cooling heat pipes according to an embodiment which is not part of the invention. Detailed description of the invention and methods of execution

[0028] With reference to the embodiments illustrated in the figures, the inductive loudspeaker 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 powered by an alternating current; one or more radially loaded magnets 5 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 loudspeaker membrane 9. Said membrane 9 is fixed to the 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 or near said coil 4.

[0029] With reference to the mode of execution illustrated in the Figures 1a And 1b , the bowl 2 is provided with fins 2a on its outer faces. On the Figure 1a , the cooling fins are oriented axially relative to the cylinder. On the Figure 1b, the cooling fins are oriented radially relative 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, achieving 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 be distributed regularly or not. They may have the same shape and / or size or not. All these parameters (and others) may be adapted according to the circumstances, the size of the bowl and / or the application.

[0030] Favorably a fan-type element, not shown on the 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 cold air around said fins 2a, so as to increase the thermal exchanges and improve the cooling of said bowl 2, magnetic air space 6 and coil 4.

[0031] With reference to the mode of execution illustrated in the Figure 2a, the bowl 2 comprises upper conduits 2b between said external medium 8 and said magnetic air space 6, as well as lower conduits 2c between said magnetic air space 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 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 fresh air coming from below from said external medium 8.

[0032] With reference to the mode of execution illustrated in the Figures 2b And 2c, the bowl 2 comprises upper conduits 2b between the under-membrane space 10 and said magnetic air space 6, as well as lower conduits 2c between said magnetic air space 10 and said external medium 8. Said conduits 2b and 2c are positioned directly opposite said coil 4, oriented in the same direction as that of the axis of said coil 4. On the Figure 2a , when the loudspeaker is in operation, said membrane 7 vibrates, which alternately creates overpressures and depressions in said under-membrane space 10, under said membrane 7. These pressures and depressions create an axial movement of air passing through said upper 2b and lower 2c conduits, thus driving out the hot air present around said coil 4 to replace it with colder air coming from said under-membrane space 10 or from said external environment 8. According to the Figure 2c, valves 11a mounted around said under-membrane space 10 can supply cold air to said under-membrane space 10.

[0033] With reference to the mode of execution illustrated in the figure 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 11b allow said under-membrane space 10 to communicate with the external environment 8. The fan 12 in operation sucks hot air around said coil 4, through said lower conduits 2c, creating a depression in said magnetic air space 10. Due to this depression, fresh air coming from said external environment 8 is sucked through said openings 11b and said upper conduits 2b to be placed around said coil 4, thus allowing it to be cooled. The Coand effect finally allows this cooling to be improved, 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 pressure and depression zones. The expansion of the air after passing through said upper duct 2b thus allows cooling of the air entering said magnetic air space 10, and therefore better cooling of said coil 4.

[0034] With reference to the mode of execution illustrated in the Figure 3, said bowl 2 is surrounded by a fluid circuit 13. In said fluid circuit 13 circulates a heat transfer fluid, favorably pure water or a dielectric liquid type “3M Novec” specially designed for the cooling of 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, achieving a cooling of 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 to a cooling system, not shown in the Figure 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.

[0035] With reference to the mode of execution illustrated in the Figure 4, said bowl 2 comprises a fluid circuit 15 on its inner face, in contact with said coil 4. In said fluid 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, achieving direct cooling thereof. Favorably, said fluid 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 fluid circuit 15, for better cooling of said coil 4.

[0036] With reference to the mode of execution illustrated in the Figures 5a And 5b, said coil 4 is made by winding an electrically conductive tube. Inside this tube 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, achieving 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 circulation of said cold heat transfer fluid in said coil 4, for better cooling thereof.

[0037] With reference to the mode of execution illustrated in the Figure 6, said bowl 2 is provided with one or more heat pipes 18 over its entire periphery. In a non-limiting manner, these heat pipes may be cylindrical in 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 higher heat exchange density than the material constituting said bowl 2. In the case of air cooling as shown in Figure 1 , or fluid 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 a greater number of calories to be evacuated to the outside.

[0038] Said cooling elements make it possible to reduce 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 inductive motor 1.

[0039] This invention can be adapted to applications other than that of the loudspeaker, particularly in applications where significant and precise vibrations must be generated over a long period of time. This is the case, for example, for vibrating pots. The principle of the invention is thus not limited to the embodiments and forms described, but is likely to be modified within the framework of the protection sought.

[0040] The methods of execution described are illustrative examples and should not be considered limiting. The methods of execution may also be combined with each other depending on the circumstances, or means used in one method may be used in another method.

Claims

1. Induction motor comprising at least one magnet (5), a mobile armature (7), a bowl (2) with a fixed coil (4) on the outside of the mobile armature (7), comprising means for cooling the fixed coil, placed outside the armature, characterized in that the coil is produced by means of a winding of an electrically conductive and hollow tube inside which a cooling heat-transfer fluid circulates.

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

3. Induction motor according to either of Claims 1 and 2, comprising cooling fins (2a) present on an outer perimeter of the bowl (2).

4. Induction motor according to one of the preceding claims, comprising openings (2b, 2c) between a magnetic air space (6) and an external environment (8), allowing a flow of air generated by chimney effect to cool the coil.

5. Induction motor according to the preceding claim, comprising a fan (12) creating a circulation of air around the coil and a reduction of temperature in the magnetic air space, the air coming from the outside and following the geometries of the coil by Coand effect, increasing the heat exchanges.

6. Induction motor according to Claim 5, comprising openings (11b) with variable sections between the external environment, the magnetic air space and / or the fan, in order to obtain a more effective cooling of the air circulating around the coil.

7. Induction motor according to one of the preceding claims, comprising a fluidic cooling circuit (15) on outer faces of the bowl (2).

8. Induction motor according to one of the preceding claims, comprising a fluidic cooling circuit on inner faces of the bowl (2), in contact with the coil.

9. Induction motor according to one of the preceding claims, comprising one or more heat pipes (18) positioned substantially radially in the bowl (2).

10. Device comprising at least one induction motor according to one of the preceding claims.

11. Device according to the preceding claim, said device being a loudspeaker or a shaker.

12. Loudspeaker according to Claim 11, comprising one or more valves (11a) between the external environment and the space under the diaphragm, so as to introduce cool air coming from the external environment.

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