DESC:TECHNICAL FIELD OF THE INVENTION
The present invention relates to an extruded housing for an electric motor and a method thereof.

BACKGROUND OF THE INVENTION
Electric motors, in general terms, consist of moving and stationary parts forming a rotor and stator of an electrical machine, with these parts being enclosed in a housing. The housing, acts to protect the moving parts, and in addition may have the function of dissipating heat that is produced by the motor. The dissipation of heat is of particular importance in high performing motors and/or in motors that are intended to be used where there are restrictions on the space and orientation required for installation of the motor.
Electric motors conventionally have been used in several industries. Electric vehicles have opened up a new avenue for application of electric motors to mobility. The nature of the motor requires that the motor is packaged inside a housing. During operation, typical electric motor operates at 80-90% efficiency, i.e. 10-20% of the electrical energy is transformed into heat. As the load on the rotor deviates further from the peak rated load, the losses tend to increase. It is important to dissipate the heat from the motor and regulate the peak temperature as it could lead to further deterioration in efficiency or complete failure of the motor. The motor housing serves a key role in dissipating- the heat efficiently and maintaining the temperature of the motor under reasonable limits.
Motor housing designs are dictated by the structural requirements like crush load, axial load bearing capacity and stiffness. Traditional designs incorporate fins in the housing to increase the surface area and increase heat dissipation capabilities of the housing. Airflow considerations decide the effectiveness of these fins. To further boost the heat dissipation, high thermal conductivity materials like aluminum alloys are used.
Die casting process limits the alloys that can be used for motor housing and the result is generally a poor conductivity alloy like ADC12 which has thermal conductivity in the range of 85-95 W/m-K. This limits the heat dissipation capacity of the housing and thereby deteriorate the performance of the motor itself.
Other functionalities that are added into the housing for electrical connections, interfacing with other structural parts of the vehicle and integration with the vehicle drivetrain. These functionalities are critical to the housing and add further complexity to the designs. Due to this complexity, motor housings for electric vehicles are traditionally manufactured using pressure die casting of aluminum alloys. In order to realize these complex designs through extrusion, the number of parts in the housing increases as shown in Fig 1. This results in an increase in complexity of assembly, alignment and tolerances.
Accordingly, there is need of a motor housing that enhances functionality without joining of multiple parts in minimal post processing.

SUMMARY OF THE INVENTION
In an aspect, the present invention provides an extruded housing for an electric motor, the housing comprising: an extruded cylindrical body for holding electrical parts of the motor, extruded axial fins formed about the outside of the cylindrical body and a plurality of functional interfaces to be connected with structural parts of a vehicle. The motor housing cover includes a main body of the housing having a plurality of fins extended longitudinally extruded by conventional hot extrusion and a plurality of functional interfaces that are printed on the main body. The fins are extruded using a high thermal conductivity, high strength Al-Mg-Si alloy. The additive manufacturing is carried out by a Wire Arc Additive Manufacturing (WAAM). The additive manufacturing is carried out by direct energy deposition. The materials used in WAAM are Al-Si or Al-Mg alloys. The motor casing exhibits up to 22% weight reduction. The thermal conductivity of the motor housing ranges between 150-200 W/m-K along with high yield strengths, ductility and toughness.

In other aspect, the present invention provides a method for manufacturing an extruded housing of an electric motor. In the first step, a housing for an electric motor is extruded along with the longitudinal fins. In the next step some machining may be done to clear area for deposition in next step. In the last step, a plurality of functional interfaces are connected to the main body by deposition through additive manufacturing thereby achieving part integration.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG 1: Conventional motor housing showing complex functionalities achieved by die casting (PRIOR ART);
FIG 2: Extruded motor housing in accordance with an embodiment of the present invention;
FIG 3: Extruded motor housing machined prior to deposition or printing
FIG. 4A shows outer diameter features and FIG. 4B shows inner diameter features of the housing of FIG. 2;
FIG. 5A and 5B show design analysis with temperature contour comparison; and
FIG.6 show graphical comparative cost analysis of extrusion-subtractive and extrusion-additive processes.

DETAILED DESCRIPTION OF THE INVENTION
As used herein, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise.
The terms "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.
As used herein, the terms "comprising" "including," "having," "containing," "involving," and the like are to be understood to be open-ended, i.e. to mean including but not limited to.
In general aspect, the present invention provides an extruded housing for an electric motor, the housing comprising: an extruded cylindrical body for holding electrical parts of the motor, extruded axial fins formed about the outside of the cylindrical body and a plurality of functional interfaces to be connected with structural parts of a vehicle deposited by additive manufacturing.
Referring to FIG. 2, in accordance with an embodiment of the present invention provides an extruded housing (20) for an electric motor (10) is shown. The housing (20) includes an extruded cylindrical body (25) for holding electrical parts of the motor (10), extruded axial fins (30) extended longitudinally outside of the cylindrical body (25) and a plurality of functional interfaces (40) to be connected with the structural parts of a vehicle. The fins (30) are not configured on a predefined portion (50) on the cylindrical body (25). The functional interfaces (40) are connected on the portion (50) by additive manufacturing thereby achieving part integration. It is to be noted here that that extruded aluminium could be used to make the housing. Al-Mg-Si alloys offer excellent thermal conductivity of 150-200 W/m-K along with high yield strengths, ductility and toughness. In an embodiment Al-Mg-Si alloy includes Al6005T6, Al6063T6, Al6082T6
In accordance with an embodiment, the motor casing of the present invention is manufactured using hybrid construction techniques. The main body of the housing (20) with fins (30) is extruded using a high thermal conductivity, high strength Al-Mg-Si alloy. The functionality is subsequently added to the extruded profile by additive manufacturing thereby achieving part integration and limiting the number of parts needed for final assembly of the housing.
Referring to FIGS. 3 to 4B, the additive manufacturing is carried out by established techniques like direct energy deposition or preferably by Wire Arc Additive Manufacturing (WAAM). The motor cover housing is manufactured, and the desired part are added or printed on the extruded housing. The materials used in WAAM are Al-Si or Al-Mg alloys. The near-net shape part may optionally be machined to achieve the final part tolerances. In accordance with an embodiment, WAAM uses a wire as feedstock that has resolution of approximately 1 mm and having deposition rate between 1 kg/hour to 10kg/hour or more depending on energy source. WAAM equipment used in the present invention is robotic or machine tool based that includes a power source for aluminium low heat input MIG.
In accordance with the embodiment, referring to FIG. 4A, for outer diameter, the deposition is carried out for bolt machining of motor housing cover and bolting to the vehicle body. Hole machining and tapping with tightening torque check is executed for thread integrity. The duty cycle with continuous deposition include 36s and 60s, each transition of approximately 4-5 mm. Weight of deposited material ranges between 60-65g. Hardness of extruded fins ranges between 72 to 85 HV0.2 and hardness of deposition ranges between 105 to 110 HV0.2.
In accordance with and embodiment, referring to FIG. 4B, deposition along inner diameter for machining step features allow thinner wall extrusion and reduce machining requirements. Inner diameter and outer diameter machining is conducted on regular lathe machine along with face milling or CNC turning machine to achieve tolerance levels. It is to be noted here that component are mounted vertically to drill ø5mm holes at PCD for depth of 20 mm followed by tapping to 10 mm depth. Components are mounted in horizontal configuration to mill deposition build up to make the flange like feature.
The present invention provides a method for manufacturing an extruded housing for electric motors. In a first step extrusion of the motor housing (20) along with fins (30) extended longitudinally is carried out. In the next step, machining of the motor housing (20) is carried out if desired. In the next step, deposition of the functional interfaces (40) is carried out by Additive manufacturing thereby achieving part integration. The last step includes machining to the final tolerances.

Examples:
Referring to Table 1 and FIG. 5A, the motor casing of the present invention exhibited up to 22% weight reduction while achieving similar or enhanced structural performance. In the embodiment, the peak temperature of the housing reduced from 102°C for conventional housing to 63°C for the housing of the present invention.
Design Material
Mass (Kg) % Weight
Saving Yield
Strength
(MPa) Peak Stress
(MPa) FOS wrt to YS
Baseline ADC12 2.17 150 40 3.75
Design
Concept 1 Al 6005
T6 1.68 22% 260
56 4.64
Table 1

Referring to Table 2 and FIG. 5B, the heat dissipation capacity of the housing (20) is enhanced by almost 35% due to significantly higher thermal conductivity of the extruded Al-Mg-Si alloy. Existing material grade is changed from ADC 12 to Al 6005 T6. Due to high strength of the Al6005T6 overall casing thickness was reduced by 1 mm i. e from 4 mm to 3 mm. 20-25% weight could be saved by this design. Weight of baseline design was 2.17 kg, and the weight of design concept was 1.163 Kg. Thermal efficiency was better than the baseline design due to high thermal conductivity of Al 6005 T6 alloy.
Material Name Density g/cm³ Tensile strength MPa Yield strength(0.2%) MPa Thermal Conductivity W/m K Hardness Brinell(HB)
ACD12 2.74 310 150 96 75
AL 6005T6 2.7 260-270 215-225 188 90
Table 2
Referring to FIG. 6, comparison between extrusion with subtraction of material and extrusion with addition of material is shown. When the motor cover housing is manufactured by extrusion process and then the extra material is removed by machining that is referred as ‘extrusion with subtraction’. On other hand, when the motor cover housing is manufactured and the desired parts are added or printed on the extruded housing is referred as ‘extrusion with addition’. It is understood from the graphical representation, that input part cost and machining part cost required for ‘extrusion with addition’ is much lesser than the input part cost and machining part cost required for ‘extrusion with subtraction’. The overall cost required for the ‘extrusion with addition’ was less than 181 units that shows economic significance along with the technical advancement as discussed above.
The description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the disclosure.

,CLAIMS:
1. An extruded housing for an electric motor, the housing comprising:
a main body (25) of the housing (20);
a plurality of fins (30) extended longitudinally on the main body (25); and
a plurality of functional interfaces (40) connected on the main body (25) by additive manufacturing thereby achieving part integration.

2. The housing as claimed in claim 1, wherein the fins (30) are extruded and the functional interfaces (40) are printed using Al-Si or Al-Mg alloy on a high thermal conductivity, high strength Al-Mg-Si alloys.

3. The housing as claimed in claim 1, wherein the additive manufacturing is carried out by a Wire Arc Additive Manufacturing (WAAM).

4. The housing as claimed in claim 1, wherein the additive manufacturing is carried out by direct energy deposition.

5. The housing as claimed in claim 3, wherein the materials used in WAAM are Al-Si or Al-Mg alloys.

6. The housing as claimed in claim 1, wherein the motor casing exhibits up to 20-25% weight reduction.

7. The housing as claimed in claims 1-6, wherein thermal conductivity of the motor housing ranges between 150-200 W/m-K along with high yield strengths, ductility and toughness.

8. A method for manufacturing an extruded housing for an electric motor, the method comprising the steps of:
extruding a main body (25) of the housing (20) along with a plurality of fins (30) extended longitudinally configured thereon; and
connecting a plurality of functional interfaces (40) on the main body (25) by additive manufacturing thereby achieving part integration.

9. The method as claimed in claim 8, wherein the additive manufacturing is carried out by a Wire Arc Additive Manufacturing (WAAM).

10. The method as claimed in claim 8-9, wherein the materials used in WAAM are Al-Si or Al-Mg alloys.