阅读说明：本技术 线圈以及电流激励式同步电机 (Coil and current-excited synchronous motor ) 是由 G·弗莱舍尔 S·塞伊斯 F·贝克 D·罗斯 C·科隆基尔 T·贝克尔 F·里施 于 2019-09-24 设计创作，主要内容包括：本发明涉及一种线圈,所述线圈包括至少局部地被环氧树脂包围的绕组,其中,在室温情况下,环氧树脂的抗压强度与其抗拉强度的比值在2至5之间,其中,在室温情况下的弹性模量为至少5000MPa,并且在环氧树脂的玻璃化温度情况下的弹性模量以及抗拉强度取值为在室温情况下的值的至少30％。(The invention relates to a coil comprising a winding which is at least partially surrounded by an epoxy resin, wherein the ratio of the compressive strength to the tensile strength of the epoxy resin is between 2 and 5 at room temperature, wherein the modulus of elasticity at room temperature is at least 5000MPa, and the modulus of elasticity and the tensile strength at the glass transition temperature of the epoxy resin take on values which are at least 30% of the values at room temperature.)

1. A coil comprising a winding at least partially surrounded by an epoxy,

wherein, under the condition of room temperature, the ratio of the compressive strength of the epoxy resin to the tensile strength thereof is between 2 and 5,

wherein the modulus of elasticity at room temperature is at least 5000MPa, and

wherein the modulus of elasticity and the tensile strength at the glass transition temperature of the epoxy resin are at least 30% of the values at room temperature.

2. The coil of claim 1, wherein the coil is a rotor of an electric machine.

3. Coil according to claim 1 or 2, wherein the glass transition temperature is at least 150 ℃, preferably at least 180 ℃.

4. Coil according to any of the preceding claims, wherein the linear thermal expansion coefficient is between 10 and 23ppm/K, preferably between 10 and 30 ppm/K.

5. Coil according to any one of the preceding claims, wherein the compressive strength at room temperature is at least 150MPa, preferably at least 200 MPa.

6. Coil according to any one of the preceding claims, wherein the tensile strength at room temperature is at least 60MPa, preferably at least 75 MPa.

7. Coil according to any of the preceding claims, wherein the modulus of elasticity at room temperature is at least 7000 MPa.

8. Coil according to any of the preceding claims, wherein the specific energy to break is at least 200J/m²Preferably at least 500J/m²。

9. The coil of any preceding claim, wherein the thermal conductivity is greater than 0.5W/mK.

10. The coil of any of the preceding claims, wherein the epoxy resin is a cycloaliphatic epoxy resin, a novolac epoxy resin, or a one-component epoxy resin with a heat-activatable latent curing agent.

11. Current-excited synchronous machine comprising a coil configured as a rotor according to any one of the preceding claims.

Technical Field

The invention relates to a coil, in particular a rotor or a stator of an electric machine, and to a current-excited synchronous machine.

Background

It is known from the prior art to embed, in particular to at least partially encapsulate, a coil, such as a stator or a rotor of an electric machine, in a casting material. Therefore, the strength or stability of the entire arrangement structure can be improved and the heat balance can be affected, and the like. In this case, the adhesion of the casting compound is often problematic. Due to the different thermal expansion coefficients of the different materials, the high operating temperatures and in particular the high forces in the rotor, separation or in general damage to the cast part can result, for example. In this connection, WO2007/036505a1 discloses a rotary electric machine having a stator which is provided with windings, wherein the winding heads of the stator are surrounded by a cast resin body, and a layer made of a flexible, thermally conductive material is provided between the cast resin body and a carrier of the stator, for example a lamination stack, which layer is intended to improve the adhesion of the cast resin body. However, the provision of such additional layers is complicated from the production point of view and the production costs become high.

Disclosure of Invention

The object of the present invention is therefore to provide a coil and a current-excited synchronous machine which are inexpensive to produce and which at the same time are compatible with optimum operating characteristics and maximum fault safety.

This object is achieved by a coil according to claim 1 and by a current-excited synchronous machine according to claim 11. Further advantages and features emerge from the dependent claims and the description.

According to the invention, the coil comprises a winding which is at least partially surrounded by an epoxy resin, in particular is injection-molded, wherein the ratio of the compressive strength of the epoxy resin to the tensile strength thereof is between 2 and 5 at room temperature, wherein the modulus of elasticity at room temperature is at least 5000MPa, and the modulus of elasticity and the tensile strength at the glass transition temperature of the epoxy resin take on at least 30% of the value at room temperature. That is, the compressive strength is advantageously adjusted or selected to be significantly higher than the tensile strength.

According to a preferred embodiment, the coil is a rotor of an electric machine, in particular a current-excited synchronous machine, which is used, for example, as a traction motor in the motor vehicle sector. It has proved unexpected here that the above-mentioned ratio is a desirable compromise, since such epoxy resins, in particular also in combination with an elastic modulus of at least 5000MPa, provide excellent strength while having a sufficiently high flexibility. Such rotors are capable of achieving rotational speeds of 17000 revolutions per minute and higher. Since the modulus of elasticity and the tensile strength at the glass transition temperature of the epoxy resin are at least 30% of the values at room temperature, a sufficient safety margin in the high and highest load range is also ensured.

According to a preferred embodiment, the glass transition temperature is at least 150 ℃, particularly preferably at least 180 ℃.

According to a preferred embodiment, the modulus of elasticity is at least 7000MPa or 8000MPa, particularly preferably in the range of 10000MPa or at least 10000MPa at room temperature. The tensile strength is preferably at least 75MPa and the compressive strength is at least 200 MPa. Preferably, the compressive strength also assumes at least 30% of the value at room temperature at the glass transition temperature. The above-mentioned ratio is also advantageously between 2.5 and 4.5 or between 3 and 4.

According to a preferred embodiment, the linear thermal expansion coefficient of the epoxy resin lies between that of copper and aluminum or steel. The stresses during operation can thus advantageously be reduced.

In particular, the linear thermal expansion coefficient is between 10ppm/K and 23ppm/K, particularly preferably between 10ppm/K and 30 ppm/K.

According to one embodiment, the compressive strength is at least 150MPa, especially preferably at least 200MPa, at room temperature.

Preferably, the tensile strength is at least 60MPa, preferably at least 75MPa, at room temperature.

As already mentioned, according to a preferred embodiment, the elastic modulus is at least 10000MPa at room temperature.

Preferably, the specific energy to break is at least 200J/m²Preferably at least 500J/m²。

The thermal conductivity is preferably greater than 0.5W/(mK), preferably greater than 0.7W/(mK), as determined by laser flash analysis.

Suitably, the epoxy resin is a cycloaliphatic epoxy resin, a novolac epoxy resin or a one-component epoxy resin with a heat-activatable latent curing agent.

The initial viscosity at 60 ℃ is preferably between 10000mPas and 20000 mPas. The initial viscosity at 90 ℃ is preferably between 3000mPas and 10000 mPas. Suitably, a gelation time of less than 20 minutes is achieved at 120 ℃.

The specific volume resistivity at 25 ℃ is preferably 10¹⁴Omega cm, wherein the electrical breakdown strength is preferably between about 20kV/mm and 30 kV/mm.

Preferably, possible fillers in the epoxy resin are non-conductive, non-magnetizable and non-abrasive.

The invention also relates to a current-excited synchronous machine comprising a coil designed as a rotor according to the invention.

The glass transition temperature is determined in accordance with DIN51007/ISO 6721/94. The modulus of elasticity and the tensile strength were determined according to ISO 527. The compressive strength was determined according to ISO604 (tests were carried out on cubes having the following dimensions: 5 mm. times.5 mm). The linear thermal expansion coefficient was determined according to DIN 51045. Specific energy to failure was determined according to ISO 178. Specific volume resistivity was determined according to IEC 60093. The electrical breakdown strength was determined according to IEC 60243-1.