Method for producing a motor flange for an electric motor

Abstract

The invention relates to a method for producing a motor flange (1) for an electric motor (2), in which - a bearing bush (3) made of steel is provided, - the bearing bush (3) is inserted into a casting mould for the motor flange (1), - the motor flange (1) is cast from aluminium, - the motor flange (1) is finished-machined together with the cast-in bearing bush (3). As a result, a cost-effective and at the same time long-lasting integration of the bearing bush (3) in the motor flange (1) can be ensured.

Description

[0001] Method for manufacturing a motor flange for an electric motor

[0002] The present invention relates to a method for manufacturing a motor flange for an electric motor. The invention also relates to a motor flange manufactured according to this method and to an electric motor with a rotor shaft mounted in such a motor flange.

[0003] Currently, a motor flange of a motor vehicle, especially an electric vehicle, consists of two separate components made of different materials: an aluminum motor flange and a steel bushing, which is pressed into the machined motor flange. A disadvantage of this design is that the pressed-in bushing can loosen during operation, leading to bearing damage and thus to the failure of the electric motor. Furthermore, to reliably achieve the required form and positional tolerances of the bushing against a bolted flange, rework may be necessary after pressing. Additionally, the heat generated during motor operation may not be adequately dissipated to the motor flange, potentially leading to overheating and failure. Moreover, manufacturing the individual bearing seats and bushings with such tight tolerances is very expensive.

[0004] From DE 197 45 725 A1, a process for producing a composite casting made of a light metal alloy, in particular a cylinder block for internal combustion engines, with a cast-in encasing, is known. One or more layers of partially molten metal alloy particles are sprayed onto the surface of the previously produced encasing. The associated mechanical impulse action destroys an oxide layer formed on the surface of the encasing, and the resulting oxide particles are distributed and incorporated into the layer. The treated encasing is placed in a mold and overmolded with the light metal alloy, a process known as the Alfinier process.

[0005] The present invention therefore addresses the problem of providing a method for manufacturing a motor flange for an electric motor which in particular avoids the disadvantages known from the prior art of a bearing bushing pressed into the motor flange.

[0006] This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0007] The present invention is based on the general concept of providing, for the first time, a so-called Alfinier process for manufacturing a motor flange for an electric motor, in which a steel bearing bushing is no longer pressed into a pre-cast and finished motor flange, as is customary, but is instead cast into the motor flange using the Alfinier process. In the inventive method for manufacturing the motor flange for an electric motor, a steel bearing bushing is first provided and then inserted into a mold for the motor flange. The motor flange is then cast from a light metal alloy, for example, an aluminum alloy, and subsequently finished together with the cast-in bearing bushing.This offers the significant advantage that the bearing bushing no longer needs to be machined on its outer diameter, as was previously the case, but can be cast in as a blank or semi-finished product. Eliminating the need for machining the bearing bushing not only saves the associated time and money, but also allows the relatively rough outer surface of the steel bearing bushing to be used to achieve better meshing with the surrounding aluminum during the Alfinier process.Furthermore, by casting the bearing sleeve directly into the motor flange, significantly improved heat transfer between the bearing sleeve and the motor flange can be achieved. This prevents overheating and, consequently, damage to the bearing sleeve, as the improved heat transfer allows the heat generated in the bearing sleeve during operation of the electric motor to be dissipated more effectively into the motor flange. After casting the bearing sleeve, the motor flange, including the bearing sleeve, is machined to its final dimensions. This ensures the extremely tight positional tolerances of 0.02 mm between a bore (hub) and a mounting flange required for rotor mounting in an electric motor. Overall, the inventive method also enables shorter and therefore more cost-effective machining times for the final machining process, while simultaneously saving material in terms of the light metal alloy.The aluminum of the motor flange and the steel of the bearing bushing are used. Furthermore, the possibility of significantly increased manufacturing accuracy allows for a longer service life and reduced wear. Another major advantage of a motor flange manufactured using the inventive method lies in its weight-optimized production, which leads to lower energy consumption and / or greater range, particularly in electric vehicles.

[0008] In an advantageous further development of the method according to the invention, a chromium-nickel steel is used for the steel of the bearing bushing. Chromium-nickel steels are extremely resistant to corrosion and also possess high wear resistance, which makes such a stainless steel particularly suitable for the use of a bearing bushing in an electric motor.

[0009] In a further advantageous embodiment of the inventive method, a chromium-molybdenum steel is used for the bearing bushing. Chromium-molybdenum steel is also a stainless steel and possesses high strength and high wear resistance, thereby ensuring smooth and low-wear bearing operation of a rotor shaft in an electric motor over the long term.

[0010] In a particularly preferred embodiment of the inventive method, the bearing bushing is inserted into the mold for the engine flange in its unmachined state. This offers the significant advantage that, firstly, the bearing bushing does not require time-consuming and costly machining, and secondly, that the bearing bushing, due to its unmachined outer surface, exhibits a higher roughness, which, when overmolded with aluminum, leads to a significantly improved interlocking and thus a significantly improved connection, particularly with regard to force and heat transmission. In a further advantageous embodiment of the inventive method, the engine flange is manufactured using gravity die casting.Gravity die casting is a casting process in which a metal mold is filled with molten metal solely by gravity. This process allows for the precise positioning and casting of metal / steel parts within the mold. Furthermore, gravity die casting offers the significant advantages of a superior surface finish and near-perfect mass uniformity among identical castings, making it particularly suitable for large-scale production. A motor flange produced using this gravity die casting method also possesses excellent mechanical properties, facilitating both the connection of the bearing bushing and the attachment to a bolt-on flange, for example, on an electric motor housing.

[0011] The motor flange and / or the bearing sleeve are expediently finished by turning, milling, and / or grinding. After casting the motor flange, it, and especially the cast-in bearing sleeve, are machined in a single setup. This allows for an extremely low form and positional tolerance of approximately 0.02 mm between a bore (hub) and a bolted flange, compared to a previously pressed-in bearing sleeve. Turning, milling, or grinding enables these extremely low form and positional tolerances to be achieved not only reliably, but also simply, with high quality, and yet cost-effectively.

[0012] The present invention is further based on the general concept of providing an engine flange manufactured according to the previous method. This allows the advantages described for the method according to the invention to be transferred to the engine flange. Specifically, the advantages of an engine flange manufactured according to the method according to the invention lie particularly in the fact that an unmachined bearing sleeve can be used, which, through overmolding with the aluminum alloy, also achieves a significantly stronger (intermetallic bond) and, with regard to heat transfer, a significantly better bond with the engine flange, thus enabling better transfer of the heat generated during operation from the bearing sleeve to the engine flange. Furthermore, the elimination of the need to machine the bearing sleeve before overmolding with the aluminum alloy allows for time and cost savings.A further advantage of the motor flange according to the invention is that it enables extremely precise form and position tolerances of only 0.02 mm between a hub and a screw-on flange, which enables not only smooth-running but also durable and low-wear bearings, in particular for a rotor shaft of an electric motor.

[0013] The present invention is further based on the general concept of providing an electric motor with a rotor shaft that is mounted in a motor flange according to the previous paragraph. This allows for the creation of an electric motor that is not only cost-effective and weight-optimized, but also wear-resistant and therefore has a long service life.

[0014] Regardless of the actual embodiment, it is clear that the cast-in bearing bushing can also be used for a bearing seat with a support and a bushing, for roller bearings, plain bearings and / or ball bearings, so that the method according to the invention can be applied to a large number of different bearing types.

[0015] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0016] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the present invention. The components of a higher-level unit, such as a device, apparatus, or arrangement, mentioned above and those to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this is depicted differently in the drawings.

[0017] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0018] They show, schematically, each one

[0019] Figure 1 shows different process steps A to D of a process according to the invention for manufacturing a motor flange according to the invention.

[0020] Figure 2 shows a motor flange according to the invention in an electric motor according to the invention.

[0021] According to Figure 1, a method according to the invention for manufacturing a motor flange 1 (compare Figure 2) for an electric motor 2 also according to the invention comprises several method steps A to D.

[0022] In the first process step A, a steel bearing bushing 3 is prepared. In the subsequent process step B, this steel bearing bushing 3 is inserted into a mold for the motor flange 1, after which the motor flange 1 is cast from aluminum in the following process step C. Of course, the motor flange 1 can also be cast from a different light metal alloy, with aluminum being particularly suitable. In the final process step D, the motor flange 1, together with the cast-in bearing bushing 3, is finished.

[0023] The inventive method offers the significant advantage that the bearing bushing 3 does not need to be machined before being cast or overmolded with the aluminum alloy in process step C, resulting in considerable time and cost savings. Furthermore, the unmachined outer surface of the bearing bushing 3 allows for a significantly improved mechanical connection between the bearing bushing 3 and the motor flange 1, or its material. Another major advantage of the bearing bushing 3 cast into the motor flange 1 using an Alfinier process is that heat transfer between the bearing bushing 3 and the motor flange 1 is significantly increased due to the intermetallic connection and the extremely close toothing. This improves heat transfer from the bearing bushing 3 to the motor flange 1 and, in particular, prevents or reduces temperature-related bearing damage.only to be feared to a significantly reduced extent.

[0024] For the steel of the bearing bushing 3, for example, a chromium-nickel steel can be used, which, in addition to high corrosion resistance, also exhibits high hardness and wear resistance. This allows a rotor shaft of the electric motor 2, for example, to be supported in the bearing bushing 3, to run smoothly and with minimal wear, resulting in a long service life for the electric motor 2. Alternatively, it is also conceivable that a chromium-molybdenum steel could be used for the steel of the bearing bushing 3, which also exhibits high wear resistance and high strength.

[0025] The recasting of the bearing bushing 3 in process step C is usually carried out using gravity die casting, which is not only a cost-effective casting process but also one suitable for large-scale production.

[0026] In process step D, in which the motor flange 1 is finished together with the cast-in bearing sleeve 3, the finishing work can be carried out, for example, by turning, milling, and / or grinding. This allows for extremely low dimensional tolerances between a bore, i.e., an inner surface 5 of the bearing sleeve 3, and, for example, a bolt-on flange 4. This results in particularly precise manufacturing of the motor flange 1 and, consequently, extremely smooth bearing operation of, for example, a rotor shaft, and thus a significantly increased service life of the electric motor 2. The shorter and more cost-effective machining time for the finishing work, achieved by eliminating the need for pre-machining the bearing sleeve 3, simultaneously saves material in terms of aluminum for the motor flange 1 and steel for the bearing sleeve 3, resulting in considerable cost advantages.

[0027] It is of course clear that the inventive method for casting the bearing bushing 3, now specified for the first time for a motor flange 1 of an electric motor 2, can not only be used for supporting a rotor shaft, but also for a bearing seat with support and bushing, for roller bearings, plain bearings and / or ball bearings.

[0028] Reference numeral list: Motor flange, electric motor, bearing bushing, screw-on flange, inner surface

Claims

Patent claims 1. Method for manufacturing a motor flange (1) for an electric motor (2), wherein - a steel bearing bushing (3) is provided, - the bearing bushing (3) is inserted into a casting mold for the motor flange (1), - the motor flange (1 ) is cast from aluminium, - the motor flange (1 ) together with the cast-in bearing bushing (3) is finished.

2. Method according to claim 1, characterized in that a chromium-nickel steel is used for the steel of the bearing bushing (3).

3. Method according to claim 1, characterized in that a chromium-molybdenum steel is used for the steel of the bearing bushing (3).

4. Method according to one of the preceding claims, characterized in that the bearing bushing (3) is inserted into the casting mold for the motor flange (1) without machining.

5. Method according to one of the preceding claims, characterized in that the motor flange (1 ) is manufactured by gravity die casting.

6. Method according to one of the preceding claims, characterized in that that the bearing bushing (3) is finished by turning, milling and / or grinding.

7. Method according to one of the preceding claims, characterized in that the motor flange (1 ) is finished by turning, milling and / or grinding.

8. Motor flange (1) manufactured according to the method of one of the preceding claims.

9. Electric motor (2) with a rotor shaft which is mounted in a bearing bushing (3) of a motor flange (1) according to claim 8.

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