Water jacket sleeve arrangement for a stator of an electric drive machine, and method for the production thereof

Abstract

The invention relates to a water jacket sleeve arrangement for a stator of an electric drive machine, comprising a water jacket sleeve for enclosing a stator outer jacket, said sleeve having a cooling structure with a plurality of axially spaced cooling fins running in the circumferential direction, wherein the water jacket sleeve has a constant wall thickness.

Description

[0001] 24-2448 DE

[0002] - 1 -

[0003] Water jacket sleeve arrangement for a stator of an electric drive machine, and methods for its manufacture

[0004] The invention relates to a water jacket sleeve arrangement for a stator of an electric drive machine, in particular for a motor vehicle, and to a method for manufacturing an electric drive machine.

[0005] Water jacket sleeves for electric drive motors are known from the prior art. These water jacket sleeves are often made of aluminum because this material has good thermal conductivity. Two main processes are used in the manufacture of such water jacket sleeves: casting and forming.

[0006] In the casting process, a water jacket sleeve is cast from aluminum. However, this method has significant disadvantages. The cylindrical shape of the sleeve requires large casting shadows, resulting in high material consumption. A considerable portion of the cast material must then be machined away, which is not only time-consuming and expensive but also leads to a high amount of material waste.

[0007] January 13, 202624-2448 DE

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[0009] Alternatively, aluminum sleeves can also be manufactured by forming. However, this process requires the use of comparatively expensive wrought alloys.

[0010] Both known manufacturing processes thus result in comparatively expensive water jacket sleeves.

[0011] Against this background, an object of the invention is to improve a water jacket sleeve arrangement for a stator of an electric drive motor and a method for its manufacture. In particular, a more cost-effective water jacket sleeve arrangement is to be provided that simultaneously ensures efficient cooling of the stator and provides stator support and torque support.

[0012] Each of the independent claims, with its features, defines an object that solves this problem. The dependent claims relate to advantageous embodiments of the invention.

[0013] According to one aspect of the invention, a water jacket sleeve arrangement for a stator of an electric drive motor of a motor vehicle comprises a water jacket sleeve for enclosing a stator outer jacket. The water jacket sleeve has a cooling structure with several axially spaced, circumferentially extending cooling fins. The water jacket sleeve, and in particular the cooling structure, has a constant wall thickness.

[0014] The constant wall thickness enables uniform heat dissipation across the entire surface of the water jacket sleeve. This results in more efficient stator cooling and prevents localized overheating. Furthermore, the constant wall thickness simplifies the manufacturing process and reduces material stresses, thus increasing the component's service life. The axially spaced cooling fins increase the surface area for heat exchange, thereby improving cooling performance. Additionally, the constant wall thickness can be a characteristic of the application of internal high-pressure forming.

[0015] January 13, 202624-2448 DE

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[0017] According to another aspect of the invention, a method for manufacturing an electric drive motor, in particular for a motor vehicle, comprises the following steps:

[0018] (i) Providing a tubular semi-finished product with constant wall thickness, (ii) forming, in particular by tensile or compressive forming, the water jacket sleeve of the water jacket sleeve assembly from the semi-finished product, forming the cooling structure, and

[0019] (iii) Forming the cooling jacket by inserting the water jacket sleeve assembly, in particular together with or separately from the stator, into an inner shell of a motor housing of the electric drive machine.

[0020] Using a semi-finished product with a constant wall thickness ensures uniform material distribution in the final product, as the wall thickness is not significantly altered during pressure forming. Forming allows the cooling structure with its cooling fins to be created in a single operation, reducing production time and costs. Flexible assembly (together with or separate from the stator) enables optimal adaptation to various production lines and motor designs.

[0021] The invention is based, among other things, on the consideration that conventional aluminum water jacket sleeves are associated with high costs. In casting, these costs arise from the cylindrical shape, which requires large casting shadows and leads to a high amount of material waste. In forming, the high costs result from the need for expensive wrought alloys.

[0022] The invention is based, among other things, on the idea of ​​manufacturing a water jacket sleeve from a tubular semi-finished product using internal high-pressure forming. Both stainless steel and aluminum can be used as the material.

[0023] A key feature of the water jacket sleeve according to the invention is that it has a substantially constant wall thickness. The use of internal high-pressure forming, as provided for in one embodiment, enables the constant wall thickness and the precise shaping of the cooling structures.

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[0026] According to one embodiment, the water jacket sleeve arrangement additionally includes a stator support sleeve with an inner side for rotationally fixed mounting of the stator and an outer side on which the water jacket sleeve is arranged.

[0027] This configuration of the water jacket sleeve arrangement allows for a clear separation of different functions: The stator support sleeve ensures the mechanical stability and precise positioning of the stator and can therefore have a greater wall thickness if necessary. The water jacket sleeve is functionally focused on the cooling function. This allows both functions to be optimized: for example, by manufacturing the stator support sleeve from a material with high mechanical strength, while a material with good thermal conductivity can be selected for the water jacket sleeve.

[0028] In an alternative design, the water jacket sleeve is radially supported on the inside of the stator support sleeve. This arrangement ensures optimal force transmission and minimizes deformation of the water jacket sleeve under thermal stress. The radial support also improves heat transfer between the stator and the cooling system, as good thermal contact is established between the components. Furthermore, this configuration simplifies assembly and allows for a compact design.

[0029] According to one embodiment, the water jacket sleeve has an inner surface designed to securely hold the stator in a rotationally fixed position. This integrated solution combines the functions of cooling and stator mounting in a single component. This reduces the number of components, simplifies assembly, and minimizes potential sources of error. Furthermore, the direct connection between the stator and the cooling structure optimizes heat transfer and increases the overall efficiency of the cooling system.

[0030] According to one design, the water jacket sleeve, particularly the cooling structure, is made of either a stainless steel alloy or an aluminum alloy. Both materials offer specific advantages. Stainless steel is characterized by high corrosion resistance, mechanical strength, and good formability, which increases the component's service life and reliability. Aluminum, on the other hand, offers excellent

[0031] January 13, 202624-2448 DE

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[0033] High thermal conductivity at low weight, which increases cooling efficiency and contributes to reducing the overall system weight.

[0034] One advantage of using a stainless steel alloy for the water jacket sleeve lies in its lower material costs compared to aluminum, as well as its good thermal conductivity, which is necessary for efficient stator cooling. An example application would be the use of an austenitic stainless steel alloy specifically designed for cold forming, such as 1.4303, or one generally intended for structural components, such as 1.4301 or 1.4401.

[0035] According to one embodiment, the water jacket sleeve, and in particular the cooling structure, is designed to be at least substantially rotationally symmetrical. This rotationally symmetrical design enables uniform cooling across the entire circumference of the stator. This prevents localized overheating and contributes to a longer service life for the electrical components. Furthermore, the rotational symmetry simplifies the manufacturing process, especially when using forming processes, leading to cost reductions in production. The symmetrical shape also facilitates assembly and ensures uniform force distribution. Additionally, the rotationally symmetrical design can be a characteristic of the application of internal high-pressure forming.

[0036] According to one embodiment, the cooling structure of the water jacket sleeve is formed by forming, in particular by tensile or compressive forming, especially pressing or bending. Forming processes such as tensile or compressive forming enable the production of complex geometries while maintaining a constant wall thickness. This is particularly advantageous for the formation of efficient cooling structures.

[0037] According to one embodiment, the water jacket sleeve and / or stator support sleeve is formed from a tubular semi-finished product. Using a tubular semi-finished product as the starting material reduces the number of manufacturing steps and minimizes material waste.

[0038] According to one embodiment, the water jacket sleeve is reshaped, in particular by tensile or compressive forming, and / or the water jacket sleeve is shaped to a 13 January 202624-2448 DE

[0039] - 6 -

[0040] The stator support sleeve is slid onto the water jacket sleeve assembly. Tensile or compressive forming allows for precise shaping of the cooling structures while maintaining material properties. This results in optimal cooling performance and mechanical stability. Sliding the water jacket sleeve onto the stator support sleeve simplifies assembly and allows for easy disassembly for maintenance. This method also ensures good thermal contact between the components, improving heat transfer.

[0041] According to one embodiment, the cooling structure features circumferential reservoirs arranged axially between the cooling fins. These circumferential reservoirs offer the technical advantage of serving as additional coolant volumes, thus increasing the heat capacity of the cooling system. Furthermore, they enable a more uniform distribution of the coolant across the entire circumference of the water jacket sleeve, resulting in more efficient and homogeneous cooling of the stator.

[0042] According to one embodiment, the water jacket sleeve is designed to form a water jacket for stator cooling, together with an outer stator jacket or an inner motor housing jacket. This configuration offers the technical advantage of a compact design, as the water jacket sleeve directly serves as the boundary of the cooling circuit. This reduces the number of components required and simplifies the assembly of the cooling system, resulting in cost savings and increased reliability.

[0043] In one embodiment, the wall thickness is constant along the entire length of the water jacket sleeve. The technical advantage of this embodiment lies in the uniform heat distribution and dissipation across the entire surface of the water jacket sleeve. This prevents localized overheating and contributes to a longer service life of the electric drive motor. Furthermore, the constant wall thickness simplifies the manufacturing process and ensures consistent mechanical strength of the sleeve.

[0044] According to one embodiment, the wall thickness is the same everywhere, i.e., it varies, for example within the limits of manufacturing tolerances, at most to the extent that it can be considered invariable for the purposes of using the invention.

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[0047] According to one embodiment, internal high-pressure forming is used as the forming process for the water jacket sleeve. This process offers the technical advantage of enabling the production of complex geometries while maintaining a constant wall thickness. It allows for the precise forming of the cooling fins and circumferential reservoirs in a single operation, thus reducing production time and costs.

[0048] Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the figures:

[0049] Fig. 1 shows a water jacket sleeve arrangement according to a first exemplary embodiment of the invention in a cut oblique view.

[0050] Fig. 2 shows a water jacket sleeve arrangement according to a second exemplary embodiment of the invention in a cut oblique view.

[0051] Fig. 3 shows a water jacket sleeve arrangement according to a third exemplary embodiment of the invention in a cut oblique view.

[0052] Figures 1 and 2 each show a water jacket sleeve assembly 100 for an electric drive motor 1 of a motor vehicle (not otherwise shown). The water jacket sleeve assembly 100 comprises a water jacket sleeve 10. The water jacket sleeve 10 extends longitudinally (with respect to the longitudinal axis L) along the stator core of a stator of the electric drive motor. The stator is indicated only by a double-dotted dashed line for the position of the stator outer jacket 4, but is otherwise not shown.

[0053] The water jacket sleeve 10 surrounds the stator (not shown), resting radially against its outer surface. In addition to the water jacket sleeve 10, the water jacket sleeve assembly 100 in both embodiments comprises only mounting flanges and coolant interfaces. Apart from the mounting flanges and coolant interfaces, the water jacket sleeve 10 is rotationally symmetrical.

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[0056] The water jacket sleeve 10 is made from a formed stainless steel tube made of a stainless steel alloy suitable for cold forming (for example 1.4303) by means of internal high-pressure forming.

[0057] The two exemplary embodiments according to Figure 1 and Figure 2 differ only slightly in the geometry of the cooling structure 20. In the embodiment according to Figure 1, a longitudinally wider, circumferential reservoir 24 is provided on both outer sides along the longitudinal axis. In the embodiment according to Figure 2, all circumferential reservoirs 24 have the same longitudinal widths.

[0058] The water jacket sleeves 10 of both embodiments are manufactured using the same production and assembly steps. First, a cylindrical, seamless stainless steel tube is provided as a semi-finished product. The water jacket sleeve 10 is then formed from this semi-finished product using internal high-pressure forming. During this process, several circumferential cooling fins 22 are formed into the semi-finished product. The constant wall thickness of the semi-finished product is maintained during the internal high-pressure forming process.

[0059] After forming, the water jacket sleeve 10 is mounted onto the stator outer jacket 4. The assembly consisting of the stator and the water jacket sleeve 10 is inserted into the motor housing at its inner shell 6. According to the geometry of the cooling structure 20, several circumferential reservoirs 24 are formed: The cooling fins 22, together with the inner shell 6 of the motor housing (indicated by the dashed lines), define these reservoirs after insertion, leaving a gap between the cooling fins 22 and the inner shell 6 through which coolant can flow axially.

[0060] In the assembled state, coolant, in this application example water, can now be circulated through the circumferential reservoirs 24 and over the cooling fins 22. The coolant enters, for example, at one axial end of the water jacket sleeve 10, flows through the cooling structure 20, absorbs heat from the stator (not shown), and exits again at the other axial end of the water jacket sleeve 10. The interaction of the circumferential cooling reservoirs 24 and the cooling fins 22 enables a turbulent coolant flow and thus efficient cooling over the entire circumference of the stator.

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[0063] The use of the cost-effective stainless steel alloy and internal high-pressure forming for the production of the water jacket sleeve 10 results in significantly lower costs compared to known aluminum solutions. At the same time, the good thermal conductivity of the stainless steel ensures sufficient cooling capacity for the stator.

[0064] Fig. 3 shows a water jacket sleeve assembly 100 for a stator of an electric drive motor of a motor vehicle in a sectional oblique view. The water jacket sleeve assembly 100 has a water jacket sleeve 10 for enclosing a stator outer jacket and a stator support sleeve 30 for rotationally fixed support of the stator in the motor housing.

[0065] The water jacket sleeve 10 extends along a longitudinal axis L and is essentially rotationally symmetrical. The water jacket sleeve 10 also features a cooling structure 20 comprising several axially spaced, circumferentially extending cooling fins 22. These cooling fins 22 increase the surface area of ​​the water jacket sleeve 10 and thereby improve heat exchange between the stator and the cooling medium. Circumferential reservoirs 24 are arranged between the cooling fins 22, ensuring efficient distribution of the cooling medium.

[0066] One feature of the water jacket sleeve 10 is its constant wall thickness d. This constant wall thickness d extends over the entire length of the water jacket sleeve 10, including the cooling structure 20. The constant wall thickness d ensures uniform heat dissipation across the entire surface of the water jacket sleeve 10 and prevents local overheating.

[0067] The water jacket sleeve 10 is made of a stainless steel alloy. The use of stainless steel offers high corrosion resistance and mechanical strength, which increases the reliability and durability of the water jacket sleeve assembly 100. In addition, the good formability of stainless steel allows for the precise formation of the cooling structure 20.

[0068] The water jacket sleeve assembly 100 also includes a stator support sleeve 30 with an inner surface 32 for rotationally fixed mounting of the stator and an outer surface 34. The water jacket sleeve 10 is arranged on the outer surface 34 of the stator support sleeve 30. This 13 January 202624-2448 DE

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[0070] The configuration allows for a clear separation of functions: The stator support sleeve 30 ensures the mechanical stability and precise positioning of the stator, whereas the water jacket sleeve 10 is designed for the cooling function.

[0071] The water jacket sleeve 10 is radially supported on the inside of the stator support sleeve 30. This arrangement ensures optimal force transmission and minimizes deformation of the water jacket sleeve 10 under thermal stress. Furthermore, the radial support improves heat transfer between the stator and the cooling system, as good thermal contact between the components is established.

[0072] The cooling structure 20 of the water jacket sleeve 10 is formed by internal high-pressure forming. In internal high-pressure forming, a high internal pressure is applied to a tubular semi-finished product to achieve the desired shape.

[0073] In the assembled state, coolant, in this application example water, can now be circulated through the circumferential reservoirs 24 and over the cooling fins 22. The coolant enters, for example, at one axial end of the water jacket sleeve 10, flows through the cooling structure 20, absorbs heat from the stator (not shown), and exits again at the other axial end of the water jacket sleeve 10. The interaction of the circumferential cooling reservoirs 24 and the cooling fins 22 enables a turbulent coolant flow and thus efficient cooling over the entire circumference of the stator.

[0074] Both the water jacket sleeve 10 and the stator support sleeve 30 are formed from a tubular semi-finished product. The use of a tubular semi-finished product as the starting material reduces the number of manufacturing steps and minimizes material waste, resulting in cost-efficient production and improved material utilization.

[0075] The water jacket sleeve arrangement 100 shown in Fig. 3 thus combines several technical advantages: It offers efficient cooling of the stator through the optimized cooling structure 20, ensures mechanical stability through the stator support sleeve 30, and enables cost-effective manufacturing through the use of stainless steel and internal high-pressure forming. The constant wall thickness d contributes to a uniform 13 January 202624-2448 DE

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[0077] Heat distribution is achieved, while the rotationally symmetrical design allows for easy assembly and even force distribution.

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[0080] REFERENCE MARK LIST

[0081] 1 Electric drive motor

[0082] 4 Stator outer casing

[0083] 6 Motor housing inner casing

[0084] 10 Water jacket sleeve

[0085] 20 Cooling structure

[0086] 22 cooling fins

[0087] 24 reservoirs

[0088] 30 Stator support sleeve

[0089] 32 Inside of the stator support sleeve

[0090] 34 Outer side of the stator support sleeve

[0091] 100 water jacket sleeve arrangement

[0092] d wall thickness

[0093] L Longitudinal axis

[0094] January 13, 2026

Claims

24-2448 DE - 13 - REQUIREMENTS 1. Water jacket sleeve arrangement (100) for a stator of an electric drive motor (1) of a motor vehicle, comprising - a water jacket sleeve (10) for enclosing a stator outer jacket (4), which has a cooling structure (20) with several axially spaced, circumferentially extending cooling fins (22), characterized by the fact that the water jacket sleeve (10), in particular the cooling structure (20), has a constant wall thickness (d).

2. Water jacket sleeve arrangement (100) according to claim 1, characterized by a stator support sleeve (30) with an inner side (32) for rotationally fixed reception of the stator and an outer side (34) on which the water jacket sleeve (10) is arranged.

3. Water jacket sleeve arrangement (100) according to claim 2, characterized in that the water jacket sleeve (10) is supported radially inside the stator support sleeve (30).

4. Water jacket sleeve arrangement (100) according to claim 1, characterized in that the water jacket sleeve (10) has an inner surface which is designed to receive the stator in a rotationally fixed manner.

5. Water jacket sleeve arrangement (100) according to one of the preceding claims, characterized in that the water jacket sleeve (10), in particular the cooling structure (20), is made of a stainless steel alloy or an aluminum alloy.

6. Water jacket sleeve arrangement (100) according to one of the preceding claims, characterized in that the water jacket sleeve (10), in particular the cooling structure (20), is rotationally symmetrical.

7. Water jacket sleeve arrangement (100) according to one of the preceding claims, characterized in that the cooling structure (20) of the water jacket sleeve (10) is formed by forming, in particular by tensile or compressive forming. January 13, 202624-2448 DE - 14 - 8. Water jacket sleeve arrangement (100) according to one of the preceding claims, characterized in that the water jacket sleeve (10) and / or stator support sleeve (30) is formed from a tubular semi-finished product.

9. A method for manufacturing an electric drive motor, in particular for a motor vehicle, comprising: - Providing a tubular semi-finished product with constant wall thickness (d), - Forming, in particular by tensile or compressive forming, the water jacket sleeve (10) of the water jacket sleeve assembly (100) from the semi-finished product, wherein the cooling structure (20) is formed, - Forming the cooling jacket by inserting the water jacket sleeve arrangement (100), in particular together with or separately from the stator, into a motor housing inner jacket (6) of a motor housing of the electric drive machine.

10. Method according to claim 9, characterized in that the water jacket sleeve (10), - in particular by tensile or compressive forming, and / or - is pushed onto a stator support sleeve (30) of the water jacket sleeve arrangement (100). January 13, 2026

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