Patent Application
20060290215
The invention relates to an electric motor and more particularly to an apparatus supporting movement of a motor shaft of an electric motor.
Electric motors often include a pair of thrust bearings to limit the movement of a motor shaft in an electric motor. One end of the motor shaft protrudes from the electric motor to communicate motion. The end of the motor shaft opposite the protruding end is often supported by a first thrust bearing that engages a tip of the shaft. The first thrust bearing limits the axial movement of the motor shaft in a first direction. A second thrust bearing often includes a first member fixed to the motor shaft and a second member fixed to a case of the electric motor. The first and second members contact one another when the motor shaft moves some predetermined distance in a second direction opposite the first direction. The first direction is away from the protruding end and the second direction is towards the protruding end. When the first and second members contact one another, the motor shaft is prevented from moving further in the second direction.
The invention provides an electric motor assembly having an electric motor with a first end and a second end spaced from the first end. The electric motor also includes a motor shaft extending along a first axis between a first tip cantilevered from the second end and a second tip spaced from the first tip along the first axis. The electric motor assembly also includes a worm gear disposed on the motor shaft between the second end and the first tip for rotation with the motor shaft about the first axis. The electric motor assembly also includes a housing having an internal surface with a first portion correspondingly shaped with respect to the first end to locate the electric motor in the housing. The housing also includes a second portion disposed along the first axis spaced from the first tip. The electric motor assembly also includes a first thrust bearing disposed between the first tip and the second portion. The first thrust bearing limits movement of the motor shaft along the first axis in a first axial direction.
Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
A plurality of different embodiments of the invention are shown in the Figures of the application. Similar features are shown in the various embodiments of the invention. Similar features have been numbered with a common reference numeral and have been differentiated by an alphabetic designation. Also, to enhance consistency, features in any particular drawing share the same alphabetic designation even if the feature is only shown in one embodiment. Similar features are structured similarly, operate similarly, and/or have the same function unless otherwise indicated by the drawings or this specification. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment unless otherwise indicated by the drawings or this specification.
Referring now to
The first thrust bearing 36 engages the first tip 22 at a bearing surface 80 and can be engaged with the second portion 34 in any manner known in the art. For example, the first thrust bearing 36 can be connected to the second portion 34 with fasteners, adhesive, snap-fit or any other permanent or releasible connection method known in the art.
The first portion 32 defines a blind aperture 82 that receives a cylindrically shaped portion of the first end 14. In alternative embodiments of the invention, the first portion 32 could includes bosses to locate the first end 14 or could define indicia to locate the first end 14.
The worm gear 26 rotates to drive one or more gears, such as gears 74; 76, 78 of a vehicle climate control system. The gears 74, 76, 78 are disposed in the housing 28 with the electric motor 12. Interaction between the worm gear 26 and the gears 74, 76, 78 urges the motor shaft 18 to move along the axis 18.
A second thrust bearing 40 is disposed adjacent to the second tip 24 along the first axis 20. The second thrust bearing 40 limits movement of the motor shaft 18 along the first axis 20 in a second axial direction 42 opposite the first axial direction 38. The motor shaft 18 is urged to move in the first axial direction 38 in response to rotation of the worm gear 26 in a first angular direction 44. The motor shaft 18 is urged to move in the second axial direction 42 in response to rotation of the worm gear 26 in a second angular direction 46 opposite the first angular direction 44. The motor shaft 18 is moveable along the axis 20. The second tip 24 is spaced from the second thrust bearing 40 during rotation of the motor shaft 18 in the first angular direction 44. Similarly, the first tip 22 is spaced from the first thrust bearing 36 during rotation of the motor shaft 18 in the second angular direction 46.
The engagement between the first tip 22 and the first thrust bearing 36 during rotation in the first angular direction 44 resists rotation of the motor shaft 18 in the first angular direction 44 at a first friction rate. The engagement between the second tip 24 and the second thrust bearing 40 during rotation in the second angular direction 46 resists rotation of the motor shaft 18 in the second angular direction 46 at a second friction rate substantially the same as the first friction rate. The first and second friction rates correspond to lost torque. The greater either of the first and second friction rates are, the greater the losses of torque.
The electric motor assembly 10 also includes a third thrust bearing 68 encircling the motor shaft 18 between the first and second tips 20, 22. The third thrust bearing 68 includes a first member 70 fixed to the motor shaft 18 and a second member 72 fixed to the second end 16. The first and second members 70, 72 contact one another in response to axial movement of the motor shaft 18 a third distance along the first axis 20. However, engagement between the first and second members 70, 72 during rotation of the motor shaft 18 in the first angular direction 44 resists rotation of the motor shaft 18 at a third friction rate higher than the first or second friction rates. As result, the torque losses occurring when the first and second members 70, 72 engage one another are higher than any torque losses occurring when the first tip 22 and the first thrust bearing 36 engage one another or when the second tip 24 and the second thrust bearing 40 engage one another. Therefore, the first thrust bearing 36 is positioned such that the first tip 22 and the first thrust bearing 36 engage one another before the first and second members 70, 72 engage one another. The engagement between the first tip 22 and the first thrust bearing 36 prevent engagement between the first and second members 70, 72. Alternative embodiments of the electric motor assembly 10 could be assembled without a third thrust bearing 68.
Referring now to
The worm gear 26a rotates to drive one or more gears, such as gears 74a, 76a, 78a of a vehicle climate control system. The gears 74a, 76a, 78a are disposed in the housing 28a with the electric motor 12a. Interaction between the worm gear 26a and the gears 74a, 76a, 78a urges the motor shaft 18a to move along the axis 18a.
Referring now to
A second thrust bearing 40a is disposed adjacent to the second tip 24a along the first axis 20a. The second thrust bearing 40a limits movement of the motor shaft 18a along the first axis 20a in a second axial direction 42a opposite the first axial direction 38a. The motor shaft 18a is urged to move in the first axial direction 38a in response to rotation of the worm gear 26a in a first angular direction 44a. The motor shaft 18a is urged to move in the second axial direction 42a in response to rotation of the worm gear 26a in a second angular direction 46a opposite the first angular direction 44a.
The engagement between the first tip 22a and the first thrust bearing 36a during rotation in the first angular direction 44a resists rotation of the motor shaft 18a in the first angular direction 44a at a first friction rate. The engagement between the second tip 24a and the second thrust bearing 40a during rotation in the second angular direction 46a resists rotation of the motor shaft 18a in the second angular direction 46a at a second friction rate substantially the same as the first friction rate. The first and second friction rates correspond to lost torque. The greater either of the first and second friction rates are, the greater the losses of torque.
Referring now to
The second portion 34a includes a first stationary cam surface 62a extending transverse with respect to the first axis 20a and a second stationary cam surface 64a extending transverse with respect to the first axis 20a. The first and second stationary cam surfaces 62a, 64a mirror one another about the first axis 20a. The first cam follower surface 50a engages the first stationary cam surface 62a and slides along the first stationary cam surface 62a during recovery of the resilient body 56a from the first configuration to the second configuration. The second cam follower surface 52a engages the second stationary cam surface 64a and slides along the second stationary cam surface 64a during recovery of the resilient body 56a from the first configuration to the second configuration.
The second portion 34a includes a first stationary cam surface 62a extending acutely with respect to the first axis 20a and a second stationary cam surface 64a extending acutely with respect to the first axis 20a. The first and second stationary cam surfaces 62a, 64a mirror one another about the first axis 20a. The first cam follower surface 50a engages the first stationary cam surface 62a and slides along the first stationary cam surface 62a during recovery of the resilient body 56a from the first configuration to the second configuration. The second cam follower surface 52a engages the second stationary cam surface 64a and slides along the second stationary cam surface 64a during recovery of the resilient body 56a from the first configuration to the second configuration. The second portion 34a also includes an aperture 66a receiving the thrust bearing and guiding movement of the thrust bearing along the first axis 20a. The aperture 66a communicates with the first and second stationary cam surfaces 62a, 64a. As a result of the cooperation between the first and second cam follower surfaces 50a, 52a with the first and second stationary cam surfaces 62a, 64a, the biasing device 48a moves along the first axis 20a toward the first tip 22a during recovery of the resilient body 56a from the first configuration to the second configuration.
The cooperation between the exemplary biasing device and the exemplary first portion 34a results in the first thrust bearing 36a being relatively lightly urged in the first axial direction 38a (against the first tip 22a) and the first thrust bearing 36a being relatively strongly urged against movement in the second axial direction 42a. With respect to the first thrust bearing 36a being relatively lightly urged in the first axial direction 38a, the biasing device 48 and the first portion 34a cooperate to easily locate the first thrust bearing 36a to contact the first tip 22a during initial assembly. The resilient body 56a recovers until the first thrust bearing 36a to contact the first tip 22a contact one another. If, during operation, the motor shaft 18 moves in the second axial direction 42a, separating the first thrust bearing 36a and the first tip 22a, the resilient body 56a can recover further to move the first thrust bearing 36a further in the second axial direction 42a. However, the cooperation between the biasing device 48 and first portion 34a does not result in a relatively strong force in the first axial direction 38a, which would increase friction between the first tip 22a and the first thrust bearing 36a and associated torque losses. On the other hand, the cooperation between the corners defined by the first and second cam follower surfaces 50a, 52a and the first and second stationary cam surfaces 62a, 64a relatively greatly resists movement of the first thrust bearing 36a in the first axial direction 38a. The corners of the first and second cam follower surfaces 50a, 52a must be driven along the sloped first and second stationary cam surfaces 62a, 64a to deform the resilient body 56a and move the first thrust bearing 36a. As result, the resistance to movement of the first thrust bearing 36a in the first axial direction 38a substantially decreases the likelihood that greater than first and second members 70a, 72a of a third thrust bearing 68a will engage one another.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
