Rotor shaft

Abstract

A rotor shaft (100) of an electric machine (650), in particular an electric machine (650) serving as a drive unit of a motor vehicle (652), is presented, via which drive power or traction power can be provided at an output. The rotor shaft comprises a rotor shaft base body (102) which has a cavity (106) that is bounded by an inner wall (108) of the rotor shaft base body (102) and through which oil can flow as a coolant, and which forms a laminated core seat (112) for a laminated core (114), a first axial end region (116) of the rotor shaft (100) and a second axial end region (118) of the rotor shaft (100), between which the rotor shaft base body (102) extends, and an oil guide tube (126) through which oil can be sprayed onto the inner wall (108) of the rotor shaft base body (102) for cooling the rotor shaft (100).In this process, a rear press section (130) of the oil guide tube (126) is pressed into a through hole (140) of the first end region (116), a front press section (136) of the oil guide tube (126) is pressed into a blind hole (138) of the second end region (118), and a main section (132) of the oil guide tube (126) is formed between the front press section (136) and the rear press section (130).

Description

Technical field

[0001] The present invention relates to a rotor shaft of an electric machine and to a method for manufacturing such a rotor shaft. State of the art

[0002] Rotor shafts are well known and usually fitted with laminated cores. These then form a rotor for an electric machine. Electric machines and their operating methods are known and proven in a wide variety of designs. One challenge is ensuring adequate cooling of the rotor shaft. One possibility is to use a fluid inside the hollow rotor shaft for cooling.

[0003] Waste heat can be detrimental in various ways. For example, the waste heat generated during the operation of an electric motor can negatively impact its efficiency, power density, and lifespan. Therefore, there is a need to dissipate heat effectively and thus achieve cooling. However, achieving satisfactory cooling is not easy, as space is relatively limited. Furthermore, cooling a technical system increases its weight, which is undesirable. The goal is to keep the weight of, for example, an electric motor as low as possible, primarily to reduce energy consumption.

[0004] There is also a need to keep the manufacturing effort as low as possible, in particular to save on materials and thus costs.

[0005] EP 1 278 290 A1 discloses a cooling structure for a rotating electric machine that demonstrates high cooling performance with a simple design. The rotating shaft of the rotating element has a hollow structure, and an inner cylindrical section, which rotates with the shaft, is provided with a cavity within the shaft. Coolant flows in this annular gap between the rotating shaft and the inner cylindrical section. In this way, the rotating element is effectively cooled with a small amount of coolant.

[0006] DE 10 2021 006 306 A1 discloses a hollow rotor shaft with a cooling insert arranged inside the shaft. The cooling insert serves to direct the coolant flow and increase the surface area. It is made of a material that has a higher thermal conductivity and a higher coefficient of thermal expansion than the rotor shaft. This is intended to improve the frictional connection between the rotor shaft and the laminated core during operation.

[0007] DE 10 2019 112 063 A1 discloses a hollow rotor shaft of an electric machine with an oil guide tube and spray openings arranged inside the shaft. Oil flowing through the oil guide tube can be sprayed onto the inner wall of the rotor shaft body via the spray openings for cooling purposes. Description of the invention

[0008] The object of the present invention is to provide a cost-effective solution for a rotor shaft of the generic type, which is improved or at least represents an alternative embodiment.

[0009] The problem is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the dependent claims, the description, and the accompanying figures. In particular, the independent claims of one claim category may also be further developed analogously to the dependent claims of another claim category.

[0010] A rotor shaft of an electric machine according to the invention comprises a rotor shaft body, a first axial end region, a second axial end region, and an oil guide tube. The rotor shaft body has a cavity bounded by an inner wall of the rotor shaft body, through which oil can flow as a coolant, and which forms a laminated core seat for a laminated core on an outer surface of the rotor shaft body. The rotor shaft body extends between the first axial end region of the rotor shaft and the second axial end region of the rotor shaft. Oil can be conveyed into the cavity of the rotor shaft body via the oil guide tube for cooling the rotor shaft. A through-hole is formed in the first end region. A blind hole is formed in the second end region. The oil guide tube has a rear pressed section and a front pressed section.A main section of the oil guide tube is formed between the front and rear press sections. The rear press section of the oil guide tube is pressed into the through hole of the first end section. The front press section of the oil guide tube is pressed into the blind hole of the second end section.

[0011] The rotor shaft can be part of an electric machine serving as a drive unit in a motor vehicle, via which drive power or traction power can be provided at an output.

[0012] The rotor shaft body, as well as the first and second end sections, can be formed in one piece. This can be achieved, for example, by first providing a solid metallic bar section as the starting material, which—that is, the starting material—extends along an axis. In a second step, the starting material can then be solidly formed by extrusion to produce a cup body. The cup body consists, firstly, of a hollow cylindrical side wall section extending axially along the axis and radially surrounding an interior space, with a hollow cylinder cross-section that remains unchanged along the axis. Secondly, the cup body consists of a transverse wall section that radially spans the interior space at an axial position along the axis.In a subsequent optional third step, the transverse wall section can be removed from the cup body—more precisely, from the side wall section—by a separation process (at least partially, and preferably completely) to produce a hollow cylinder body formed (preferably solely) by the side wall section, serving as the rotor shaft base. In a subsequent fourth step, at least one axial section of the hollow cylinder body is swaged to form the rotor shaft. This bulk forming process results in a surface with very good roughness values ​​and very high dimensional and geometric accuracy; this has a significant economic impact, especially with high production volumes (for example, several tens of thousands to several million components per year).The rotary swaging process and the associated elongation of the material result in a particularly high quality of the rotor shaft sections in question – for example, compared to machining. The pre-material or raw material can preferably be made of iron, an iron alloy such as steel, aluminum, or an aluminum alloy. In principle, the pre-material or raw material can be made of any material that is suitable for a rotor shaft and can be subjected to the aforementioned process steps for its formation. Thus, all possible iron-like materials and other metallic materials are also conceivable.

[0013] This allows the material to be optimally selected according to the desired purpose and area of ​​application.

[0014] Alternatively, the rotor shaft body and the second end section can be formed in one piece, and the first end section can be positively and / or non-positively connected to the rotor shaft body. In particular, the first end section can be pressed into the rotor shaft body. As described above, the pre-material can be solidly formed in one step by extrusion to produce a cup body, whereby the rotor shaft body and the second end section are formed together. The first end section can be formed separately in a separate step. Subsequently, the first end section can be pressed into the cup body to be positively and / or non-positively connected to the rotor shaft body.

[0015] The rear press section can have a larger outer diameter than both the main section and the front press section. In particular, the outer diameter of the main section and the outer diameter of the front press section can be the same. This allows the front press section and the main section to be easily inserted through the through-hole and pressed in simultaneously. The through-hole can have a uniform diameter along its entire length in the first end region. Alternatively, the through-hole can have at least two different diameters, with the diameter in the section of the press fit containing the oil guide tube being smaller than the diameter in the rest of the through-hole. This allows the oil guide tube to be easily inserted up to the point where it is then pressed in.

[0016] The rear pressed section can be expanded. This can be done in a single step of flaring and / or swaging and / or necking. In this way, a "simple" pipe can be expanded cost-effectively in a specific area, in this case the (rear) pressed section, to a larger outer diameter. The rear pressed section of the oil guide pipe can be expanded using forming techniques.

[0017] An outlet section can be formed between the main section and the front press section. This outlet section can have at least one through-opening through which oil from the oil guide tube can flow into the interior of the rotor shaft core cavity. In particular, multiple through-openings, for example two, three, four, or five, can be provided. These through-openings can be round. This allows for cost-effective manufacturing of the outlet section. The through-openings can be produced, for example, by stamping. They can also be machined, for example, by drilling.

[0018] The rotor shaft body can be coupled to a transmission shaft at its first axial end. The rotor shaft body can be supported at its first axial end via the transmission shaft. The rotor shaft body can be supported at its second axial end via a bearing acting there.

[0019] A method according to the invention for manufacturing a rotor shaft comprises at least the following steps: Providing a rotor shaft body having a cavity bounded by an inner wall of the rotor shaft body and through which oil can flow as a coolant, and forming a laminated core seat for a laminated core, with a first axial end region of the rotor shaft and a second axial end region of the rotor shaft between which the rotor shaft body extends, wherein a through hole is formed in the first end region and a blind hole is formed in the second end region, and Providing an oil guide tube through which oil can be sprayed onto the inner wall of the rotor shaft body for cooling the rotor shaft, wherein the oil guide tube has a rear press section at a first end region of the oil guide tube and a front press section at a second end region of the oil guide tube, wherein a main section of the oil guide tube is formed between the front press section and the rear press section, and pressing the rear press section of the oil guide tube into the through hole of the first end region, and the front press section of the oil guide tube into the blind hole of the second end region.

[0020] The step of providing the rotor shaft body can include a bulk forming step. The pre-material or raw material can preferably have a cylindrical – i.e., a fully cylindrical – shape. Such a pre-material or raw material can be easily manufactured and subsequently processed. A circular cylindrical – i.e., a fully circular cylindrical – shape is particularly preferred, as this most closely approximates the often desired rotationally symmetrical shape of a rotor shaft and thus potentially requires the least material forming. In principle, other cross-sectional shapes of the pre-material or raw material are also conceivable, such as a square or rectangular cylindrical shape, which, for example, allows for particularly compact storage and transport of multiple pieces of the pre-material or raw material.The raw material can then be solidly formed by extrusion to produce a cup body. The extrusion process can preferably be cup extrusion. Cup extrusion allows for the particularly simple production of the aforementioned cup body, creating the hollow cylindrical side wall section with the transverse wall section extending transversely within the interior. In principle, the extrusion can also be hollow extrusion. However, hollow extrusion alone can sometimes entail higher manufacturing costs and more post-processing, and consequently, higher material consumption compared to cup extrusion alone. It is conceivable that the extrusion process is preferably carried out in multiple stages, for example, combining cup and hollow extrusion.Preferably, the extrusion process can be a forward cup extrusion and / or a backward cup extrusion. In particular, backward cup extrusion has proven especially advantageous, as it yields particularly favorable results with regard to material quality and the produced cup body on the one hand, and tool wear on the other. A transverse cup extrusion process is also conceivable in principle.

[0021] Bulk forming refers to a forming process in which a three-dimensional material flow occurs and different wall thicknesses can be achieved in the component. Extrusion is a specific type of bulk forming without flash. Cold extrusion refers to an extrusion process in which the workpiece is at approximately room temperature before forming begins, i.e., it is not heated before the forming process.

[0022] The extrusion process can preferably be cold extrusion. Cold extrusion produces a surface with particularly good roughness values ​​and exceptionally high dimensional and geometric accuracy, making it especially economically advantageous for high production volumes of tens of thousands to several million components per year.

[0023] The step of providing the oil guide tube may include a step of expanding the rear press section so that the rear press section has a larger outside diameter than the outside diameter of the main section and the outside diameter of the front press section. Specifically, the outside diameter of the main section and the outside diameter of the front press section may be the same. Brief character description

[0024] The inventive idea will be described in more detail below with reference to the figures. However, the following description should be considered purely exemplary. The invention is defined solely by the subject matter of the claims. Advantageous embodiments of the invention are explained below with reference to the accompanying figures. The same reference numerals are used for identical or equivalent elements. Furthermore, for the sake of readability and identifiability, reference numerals are also used for features that are not shown in the described figure. Similarly, not all reference numerals are always drawn in comparable figures if these features are already clearly identified in the preceding figures. The figures show: Fig. 1 a sectional view of a rotor shaft of an electric machine according to an embodiment of the present invention; Fig. 2 a sectional view of an oil guide tube for a rotor shaft according to an embodiment of the present invention; Fig. 3 a sectional view of a rotor shaft of an electric machine according to a further embodiment of the present invention; Fig. 4 an excerpt of the in Fig. 3 rotor shaft shown according to a further embodiment of the present invention; Fig. 5a another excerpt of the in Fig. 3 rotor shaft shown according to a further embodiment of the present invention; Fig. 5b a section of a rotor shaft according to a further embodiment of the present invention; Fig. 5c a section of a rotor shaft according to a further embodiment of the present invention; Fig. 6 a vehicle according to an embodiment of the present invention; and Fig. 7 a flowchart of a method according to the invention in accordance with an embodiment of the present invention. Detailed character description and description of the invention

[0025] Fig. Figure 1 shows a sectional view of a rotor shaft 100 of an electric machine. The rotor shaft 100 has a rotor shaft body 102, a first end section 116, and a second end section 118. The rotor shaft body 102 has a cavity 106. This allows for a lightweight rotor shaft 102 that can be cooled by oil. The rotor shaft body 102 is tubular in shape, and the two axial end sections 116 and 118 have a smaller outer diameter, on which the rotor shaft 100 can be supported (via a first bearing section 118 on the first end section 116 and a second bearing section 122 on the second end section 118). A laminated core seat 112 is formed in a main section 104 on an outer wall 110 of the rotor shaft body 102. A laminated core 114 is arranged on this seat.

[0026] In the first end region 116, a through-hole 140 is formed in the axial direction. In the second end region 118, a blind hole 138 is formed. An oil guide tube 126 is arranged between these two end regions 116 and 118. The oil guide tube 126 is in Fig. 2 shown separately. The oil guide tube 126 has a front press section 136 and a rear press section 130, with a main section 132 extending between them. An outer diameter D HA of the main section 132 and an outer diameter D vP The dimensions of the front press section 136 are the same. An outer diameter D hP The diameter of the rear press section 130 is larger than the outer diameter D. HA of the main section 132 and the outer diameter D vPof the front press section 136. The inner diameter of the blind hole 138 is dimensioned such that, in conjunction with the front press section 136, it forms an interference fit between the oil guide tube 126 and the second end section 118. The inner diameter of the through hole 140 is dimensioned such that, in conjunction with the rear press section 130, it forms an interference fit between the oil guide tube 126 and the first end section 116. The interference fits create mechanically stable connections; optionally, these are designed to be fluid-tight.

[0027] The oil guide tube 126 has an outlet section 134 near the front press section 136, in particular between the front press section 136 and the main section 132 of the oil guide tube 126. This can be achieved by at least one through-opening in the oil guide tube 126, in particular two, three, four, or more through-openings. These through-openings can be designed as bores. Optionally, further outlet openings can also be provided in the main section 132. If there are multiple outlet openings in the oil guide tube 126, these can have different diameters or cross-sections to generate optimal cooling performance.

[0028] The rotor shaft body 102 is formed integrally with the second end section 118. The first end section 116 is either formed integrally or alternatively by positive and / or force-fit connection with the rotor shaft body 102. This allows for the selection of an optimal manufacturing process depending on the geometry.

[0029] The rotor shaft body 102 has at least one outflow opening 144 adjacent to the lamination stack seat 112. If there are multiple outflow openings 144, these are preferably evenly distributed around the circumference.

[0030] Fig. Figure 3 shows a sectional view of a rotor shaft 100 of an electric machine according to a further embodiment of the present invention. In this embodiment, the rotor shaft body 102 is formed in two parts. A first part of the rotor shaft body 102 is formed integrally with the first end region 116. A second part of the rotor shaft body 102 is formed integrally with the second end region 118. The two parts of the rotor shaft body 102 are joined together by a material bond, in particular by welding.

[0031] Fig. 4 and Fig. Figures 5a each show a section of the Fig. 3. Rotor shaft 100 shown. In this alternative embodiment, the through-hole 140 is longer compared to the previously shown embodiment and has an inlet area and a press area. Furthermore, a variant of the oil guide tube 126 is shown here in which the inner diameter is constant over the entire tube length and the outer diameter is widened in the area of ​​the rear press section 130. These two features can also be described individually with the one in Fig. 1 and Fig. 2 can be combined with the illustrated embodiment.

[0032] Fig. 5b and Fig. Figure 5c shows alternative embodiments for the second end section 118 according to embodiments of the present invention. A press fit exists between the oil guide tube 126 and the second end section 118. A press fit is a force-fit connection of two parts that utilizes the friction between these two parts. It is classified as a press-fit and press-in connection and is standardized by DIN 8593. In the embodiment shown above, this is designed as a transverse press fit. The [unclear text] Fig. The embodiment shown in section 5b depicts a transverse press fit, wherein the two connecting partners are arranged in reverse, i.e. the oil guide tube 126 is pressed onto a press-fit bolt 139a.

[0033] Fig. Figure 6 shows a vehicle 652 according to an embodiment of the present invention. The vehicle 652 has an electric machine 650. The electric machine 650 is an electric machine serving as a drive unit. Drive power or traction power for the vehicle 652 can be provided via an output of the electric machine. An embodiment of the previously described rotor shaft 100 is used in the electric machine 650.

[0034] Fig.Figure 7 shows a flowchart of a method according to an embodiment of the present invention. The method comprises at least two provisioning steps and one pressing-in step. In one provisioning step, the rotor shaft base body 102 with the two end regions 116 and 118 is provided; in a further provisioning step, the oil guide tube is provided. The latter is then inserted through the through-hole 140 in the pressing-in step, and then the rear press section 130 of the oil guide tube 126 is pressed into the through-hole 140 of the first end region 116, and the front press section 136 of the oil guide tube 126 is pressed into the blind hole 138 of the second end region 118.

[0035] The provisioning step can include one or more bulk forming steps. The provisioning step of the oil guide tube 126 optionally includes a step of expanding the rear press section 130, such that the rear press section 130 has a larger outer diameter D. hP has an outer diameter D HA of the main section 132 and an outer diameter D vP of the front press section 136. The outer diameter D is optional. HA of the main section 132 and the outer diameter D vP of the front press section 136 same. Reference symbol list 100 rotor shaft 101 Rotor 102 Rotor shaft base bodies 104 Main section, sheet metal package seat area 106 cavity 108 Interior wall 110 Exterior wall 112 Sheet metal package seat 114 sheet metal package 116 First end area 118 Second end area 120 First storage area 122 Second storage area 124 Outlet 126 Oil guide tube 128 Inlet opening 130 rear press section (especially widened or flared) 132 Main Section 134 Outflow section 136 front press section 138 blind hole 139 Press seat device 139a Press-fit bolt 140 through hole 142 Drive 144 Outlet 650 electric machine 652 Vehicle, motor vehicle S1-S3 process steps QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 1 278 290 A1

[0005] DE 10 2021 006 306 A1

[0006] DE 10 2019 112 063 A1

[0007]

Claims

[1] Rotor shaft (100) of an electric machine (650), in particular an electric machine (650) serving as a drive unit of a motor vehicle (652), comprising at least - a rotor shaft body (102) which has a cavity (106) which is bounded by an inner wall (108) of the rotor shaft body (102) and through which oil can flow as a coolant, and which forms a laminated core seat (112) for a laminated core (114), - a first axial end region (116) of the rotor shaft (100) and a second axial end region (118) of the rotor shaft (100), between which the rotor shaft body (102) extends, and - with an oil guide tube (126) through which oil can be directed into the cavity (106) of the rotor shaft base body (102) for cooling, - wherein a rear press section (130) of the oil guide tube (126) is pressed into a through hole (140) of the first end region (116), a front press section (136) of the oil guide tube (126) is connected to the second end region (118), and a main section (132) of the oil guide tube (126) is formed between the front press section (136) and the rear press section (130). [2] Rotor shaft (100) according to claim 1, wherein the rotor shaft body (102) and the first end region (116) and the second end region (118) are formed in one piece. [3] Rotor shaft (100) according to claim 1, wherein the rotor shaft base body (102) is formed integrally with the second end region (118), and the first end region (116) is connected to the rotor shaft base body by a form-fit and / or force-fit connection, in particular by a press fit. [4] Rotor shaft (100) according to one of the preceding claims, wherein the front press section (136) of the oil guide tube (126) is pressed with the second end region (118), wherein the second end region (118) has a blind hole (138) into which the front press section (136) is pressed, or wherein a bolt-shaped contact area (139) is formed on the second end region (118) and the front press section (136) is pressed onto the bolt-shaped contact area (139). [5] Rotor shaft (100) according to one of the preceding claims, wherein the rear press section (130) has a larger outer diameter (D hP ) has an outer diameter (D HA ) of the main section (132) and an outer diameter (D vP ) of the front press section (136), and in particular the outer diameter (D HA ) of the main section (132) and the outer diameters (D vP ) of the front press section (136) are the same. [6] Rotor shaft (100) according to one of the preceding claims, wherein the rear press section (130) is widened. [7] Rotor shaft (100) according to one of the preceding claims, wherein an outlet section (134) is formed between the main section (132) and the front press section (136). [8] Method for manufacturing a rotor shaft (100) according to any one of the preceding claims, comprising at least the following steps: - Providing a rotor shaft body (102) having a cavity (106) bounded by an inner wall (108) of the rotor shaft body (102) and through which oil can flow as a coolant, and forming a laminated core seat (112) for a laminated core (114), with a first axial end region (116) of the rotor shaft (100) and a second axial end region (118) of the rotor shaft (100) between which the rotor shaft body (102) extends, wherein a through hole (140) is formed in the first end region (116) and a blind hole (138) is formed in the second end region (118), and - Providing an oil guide tube (126) through which oil can be directed into the cavity (106) of the rotor shaft body (102) for cooling the rotor shaft (100), wherein the oil guide tube (126) has a rear press section (130) at a first end region of the oil guide tube (126) and a front press section (136) at a second end region of the oil guide tube (126), wherein a main section (132) of the oil guide tube (126) is formed between the front press section (136) and the rear press section (130), and - Pressing the rear press section (130) of the oil guide tube (126) into the through hole (140) of the first end section (116) [9] Method according to claim 8, wherein the step of providing the rotor shaft base body (102) comprises a bulk forming step. [10] Method according to claim 8, wherein the step of providing the oil guide tube (126) comprises a step of widening the rear press section (130) such that the rear press section (130) has a larger outer diameter (D hP ) has an outer diameter (D HA ) of the main section (132) and an outer diameter (D vP ) of the front press section (136), in particular wherein the outer diameter (D HA ) of the main section (132) and the outer diameters (D vP ) of the front press section (136) are the same.

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