Transmission and electric drive system with a transmission

Abstract

Gearbox with a sealed housing, wherein a thermal expansion compensation material with a negative coefficient of thermal expansion is arranged inside the housing of the gearbox, characterized in that the thermal expansion compensation material is scandium trifluoride.

Description

[0001] The invention relates to a gearbox and an electric drive system with a gearbox.

[0002] Gearboxes with a sealed housing are known in the prior art. Such gearboxes with sealed housings have the advantage that the sealing protects the interior of the gearbox from environmental influences. Furthermore, it prevents operating fluids, such as oils, that may be present inside the gearbox from escaping.

[0003] During operation, gearboxes are often subject to significant temperature changes. In practice, this often leads to fluids inside the gearbox expanding as the gearbox's operating temperature increases. This can cause a pressure increase in the fluids trapped within the gearbox housing, particularly the air and / or gearbox oil. This pressure increase, in turn, can lead to a failure of the gearbox housing seal; for example, a leak may occur in the area of ​​a shaft penetration.

[0004] To counteract this, pressure equalization devices, such as venting elements, are known according to the state of the art, which enable pressure equalization or at least a reduction of the pressure difference between the inside of the gearbox housing and the environment of the gearbox.

[0005] However, the exchange of air between the inside of the gearbox housing and the surrounding environment, which accompanies pressure equalization, inevitably leads to the potential negative effects of the ambient air on the gearbox components located inside the housing, or even intensifies them. For example, regular air exchange with the environment can accelerate the aging of the oil inside the gearbox.

[0006] Furthermore, such pressure equalization devices or venting elements place increased demands on the gearbox installation. The spatial orientation in which the gearbox is installed may need to be taken into account to ensure that the pressure equalization device or venting elements function correctly.

[0007] JP 2023 - 063 913 A shows a gearbox with a sealed housing, wherein zirconium tungstate is arranged inside the gearbox housing as a thermal expansion compensation material with a negative coefficient of thermal expansion.

[0008] The CN 103 953 696 A shows a gearbox in which hydrogels are used for power transmission.

[0009] The object of the present invention is therefore to demonstrate a gearbox and an electric drive system with such a gearbox in which the aforementioned disadvantages do not occur or at least occur to a reduced extent.

[0010] The problem is solved by a gearbox and an electric drive system with the features of the independent claims. The features of the dependent claims relate to advantageous embodiments.

[0011] The problem is solved by a gearbox with a sealed housing. In this context, a sealed housing is understood to mean, in particular, a housing designed to be so tightly sealed that no exchange of substances occurs between the interior of the housing and its environment, or at least no exchange of substances between the interior of the housing and its environment beyond diffusion processes, during the gearbox's intended use. Intended use, in this context, refers specifically to the standard operating conditions for which the gearbox is intended.

[0012] The problem is solved, in particular, by arranging a thermal expansion compensation material with a negative coefficient of thermal expansion inside the gearbox housing. Such a thermal expansion compensation material, placed inside the housing, reduces its volume with increasing temperature. This provides a larger volume inside the housing, which can be occupied by expanding materials as the temperature rises. The pressure increase inside the housing resulting from a rise in gearbox temperature can thus be compensated for or at least reduced. This can, in particular, mean that air exchange with the environment for pressure equalization is no longer necessary, or at least only required to a lesser extent.

[0013] The housing can be sealed against a shaft, in particular. This sealing can be achieved, in particular, by means of a shaft seal. Such seals between a housing and a shaft present a challenge due to the relative movements of the sealing components and the resulting pressure differences, especially when a certain degree of smooth operation with respect to these relative movements is required. Against this background, the present invention is particularly advantageous for use in such gearboxes or electric drive systems.

[0014] The quantity of the thermal expansion compensating material can be dimensioned such that its negative thermal expansion compensates for at least 30%, and in particular at least 50%, of the positive thermal expansion of the fluids present in the gearbox when the gearbox temperature rises from room temperature and / or a temperature of 20°C to the gearbox's operating temperature and / or a temperature of 80°C. It has been shown that such a dimensioning of the quantity of thermal expansion compensating material often provides sufficient relief from the pressure increase inside the gearbox.

[0015] Gear oil may be present inside the housing. Particularly in gearboxes containing gear oil, the use of a thermal expansion compensation material can be advantageous, as at least reduced air exchange with the environment counteracts premature aging of the gear oil.

[0016] The quantity of the thermal expansion compensating material can be dimensioned such that its negative thermal expansion compensates for at least 30%, and in particular at least 50%, of the positive thermal expansion of the gear oil present in the gearbox when the gearbox temperature rises from room temperature and / or a temperature of 20°C to the gearbox's operating temperature and / or a temperature of 80°C. It has been shown that such a dimensioning of the quantity of thermal expansion compensating material often provides sufficient relief from the pressure increase inside the gearbox, especially when a gearbox contains a large quantity of gear oil.

[0017] A certain amount of air may be trapped within the housing. Particularly in gearboxes containing trapped air, the use of a thermal expansion compensation material can be advantageous, as this material counteracts the comparatively large thermal expansion of the air.

[0018] The quantity of the thermal expansion compensating material can be dimensioned such that its negative thermal expansion compensates for at least 30%, and in particular at least 50%, of the positive thermal expansion of the air trapped within the gearbox when the gearbox temperature rises from room temperature and / or a temperature of 20°C to the gearbox's operating temperature and / or a temperature of 80°C. It has been shown that such a dimensioning of the quantity of thermal expansion compensating material often provides sufficient relief from the pressure increase inside the gearbox, especially when a gearbox contains a large amount of trapped air.

[0019] The thermal expansion compensation material is scandium trifluoride. In practice, this material has demonstrated suitable thermal expansion behavior with a negative coefficient of thermal expansion, making it fundamentally suitable as a thermal expansion compensation material.

[0020] The electric drive system comprises an electric motor and a gearbox of the type described above. Such electric drive systems are used, for example, as drives in machines where they are subject to high demands regarding reliability and service life. Therefore, thermal expansion compensation materials can be particularly advantageous in the gearboxes of such electric drive systems.

Claims

[1] Gearbox with a sealed housing, wherein a thermal expansion compensation material with a negative coefficient of thermal expansion is arranged inside the housing of the gearbox, characterized by that the thermal expansion compensation material is scandium trifluoride. [2] Gearbox according to claim 1, characterized by , that the housing is sealed against a shaft, in particular with a shaft seal ring that acts in a sealing manner with the shaft. [3] Gearbox according to any of the preceding claims, characterized by, that the quantity of the thermal expansion compensation material is dimensioned such that the negative thermal expansion of the thermal expansion material compensates the positive thermal expansion of the fluids present in the gearbox when the temperature of the gearbox increases from room temperature and / or a temperature of 20°C to the operating temperature of the gearbox and / or a temperature of 80°C by at least 30%, in particular by at least 50%. [4] Gearbox according to any of the preceding claims, characterized by that there is gear oil inside the housing. [5] Gearbox according to claim 4, characterized by, that the quantity of the thermal expansion compensation material is dimensioned such that the negative thermal expansion of the thermal expansion material compensates the positive thermal expansion of the gear oil at least 30%, and in particular at least 50%, when the temperature of the gear increases from room temperature and / or a temperature of 20°C to the operating temperature of the gear and / or a temperature of 80°C. [6] Gearbox according to any of the preceding claims, characterized by , that there is a quantity of air enclosed within the housing. [7] Gearbox according to claim 6, characterized by, that the quantity of the thermal expansion compensation material is dimensioned such that the negative thermal expansion of the thermal expansion material compensates the positive thermal expansion of the amount of air enclosed in the housing when the temperature of the gearbox rises from room temperature and / or a temperature of 20°C to the operating temperature of the gearbox and / or a temperature of 80°C by at least 30%, in particular by at least 50%. [8] Electric drive system comprising an electric motor and a gearbox according to one of the preceding claims.