Electrical motors, such as actuator motors used in automotive applications, typically include a metal pole housing configured to receive magnets and an armature to form the electric motor. These metal pole housings are used to maintain a magnetic circuit of the electric motor in a closed field or loop manner. Therefore, the motor operates by having the armature turn inside the pole housing when a voltage is supplied to the motor. Metal pole housings are produced using a variety of different manufacturing processes. For example, the pole housings may be formed by a deep drawn stamping process, a rolling process, an extrusion process, or other forming process. The cost of an electric motor changes significantly depending upon the type of manufacturing process used for the metal pole housings.
Typically, a deep drawn stamping process is used to manufacture metal motor pole housings used in applications where water sealing is required. Deep drawn metal stamping processes are very specialized and sophisticated. Therefore, very few suppliers are able to meet an established stringent engineering requirement. As a result, product design and tooling costs are very high for such deep drawn metal stamping designs.
The costs of such metal pole housings are further increased if sintered bushings are required. These bushings are commonly used in electric motors to support the motor armature shaft. In addition, plastic end plugs or thrust buttons for the armature shafts may also be required with metal pole housings. Such plastic end plugs or thrust buttons locate a specific broach pocket for the shaft and reduce rubbing and thumping noises during operation of the motor by avoiding asperity contact between the metal shaft of the armature and the metal pole housing.
Rolled metal pole housings are often used for electric motors where water sealing is not a requirement. Since the rolling or forming process is a relatively simple process, design and tooling costs are much less than those associated with the deep drawn stamping processes. However, pole housings made using the rolling process are not water tight. Therefore, such rolled pole housings are typically used only for unsealed applications. Sintered bushings and/or armature shaft end plugs are also used with the rolled pole housings which further increase the costs of these housings.
In order to overcome some of the problems associated with metal pole housings, plastic pole housings for electric motors have recently been introduced. The present invention provides improvements to such plastic pole housings for electric motors. The present invention provides significant costs advantages especially compared to deep drawn metal stamping processes. The present invention also provides a plastic pole housing which meets water sealing requirements so that the plastic pole housing of the present invention may be used in applications where rolled metal pole housings typically cannot be used. The present invention also improves sound damping characteristics and reduces weight as compared to conventional metal pole housings.
In an illustrated embodiment of the present invention, a housing assembly for an electric motor comprises a sealed plastic enclosure including a body portion having a nose and an open end opposite from the nose. The open end provides access to an interior region of the plastic enclosure. The housing assembly also comprises a metal sleeve located within the interior region of the plastic enclosure, and a magnet structure located within an interior region of the metal sleeve.
In an illustrated embodiment, the plastic enclosure is formed from a material capable of operating at temperatures ranging from about −40° C. to about 85° C. Illustratively, the plastic enclosure is formed from a material capable of withstanding a thermal shock of at least 110° C.
In another illustrated embodiment of the present invention, a housing assembly for an electric motor comprises a plastic enclosure including a body portion having an outer surface and an inner surface defining an interior region. The body portion also has a nose and an open end opposite from the nose. The open end provides access to the interior region of the plastic enclosure. The housing assembly also comprises a plurality of crush ribs formed on the inner surface of the plastic enclosure, a metal sleeve located within the interior region of the plastic enclosure, and a magnet structure located within an interior region of the metal sleeve. The metal sleeve is configured to engage the plurality of crush ribs.
In an illustrated embodiment, the crush ribs include a lead-in ramp surface located adjacent the open end of the plastic enclosure and an elongated body portion extending longitudinally along the inner surface of the plastic enclosure. In one embodiment, the plastic enclosure is sealed to prevent water from entering the interior region of the plastic enclosure.
In yet another illustrated embodiment of the present invention, a housing assembly for an electric motor comprises a plastic enclosure including a body portion having a nose and an open end opposite from the nose. The open end provides access to an interior region of the plastic enclosure. The housing assembly also comprises a metal sleeve located within the interior region of the plastic enclosure, the metal sleeve being formed from separate first and second metal sheets, and a magnet structure located within an interior region of the metal sleeve.
In an illustrated embodiment, the first and second separate metal sheets include tabs configured to couple the first and second metal sheets together to form the metal sleeve. In one embodiment, the first and second metal sheets are identically shaped.
Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.