Patent Application
20200284296
The present disclosure relates to an actuator having a gear train, and more particularly, to a gear assembly of the gear train.
Motorized actuators utilized, for example, in the automotive industry have a wide range of applications, and may be applied to any mechanical device requiring a specific motion. For example, motorized actuators are utilized in EGR valves, throttle bodies, variable vane turbocharges, and other applications. Such actuators are often small with packaging and cost restraints, while needing to be robust and reliable in design. Unfortunately, known actuators use ball bearings to provide friction free rotation of internal gear shafts. Various load and vibration forces may wear upon such bearing and other components limiting the actuators useful life.
For example, known ball bearing assemblies used in such actuators have an outer periphery, or race, that is press fitted to an actuator housing, and an inner periphery, or race, of the ball bearing assembly is press fitted to the gear shaft. Consequently, axial movement of the shaft is limited by the ball bearing assembly, which must absorb axial forces. This axial absorption may reduce the useful life of the ball bearing assembly.
Accordingly, it is desirable to provide more robust actuator designs within packaging and cost restraints.
According to one, non-limiting, exemplary embodiment of the present disclosure, a gear train includes a housing, a gear, a shaft, a needle bearing, and a stop shim. The housing includes an end face traversing an axis and a cylindrical surface centered to the axis. The face and the surface defines a bore. The gear is disposed in the housing, and is adapted to rotate about the axis. The shaft is engaged to, and projects axially from, the gear. The shaft includes an end portion disposed in the bore. The needle bearing is seated in the bore, and is disposed radially between the surface and the end portion. The stop shim is disposed axially between the end face and the end portion for limiting axial displacement of the gear shaft. The stop shim is made of a material that is harder than a material of the housing.
In accordance with another embodiment, a gear train includes a housing, a gear, a gear shaft, and a bearing assembly. The housing includes an end face traversing an axis and a cylindrical surface centered to the axis. The end face and the cylindrical surface define a bore. The gear is disposed in the housing, and is adapted to rotate about the axis. The gear shaft is engaged to, and projecting axially from, the gear. The gear shaft includes an end portion disposed in the bore. The bearing assembly includes a cylindrical bearing race seated in a bore, and a plurality of needle bearing elements disposed radially between the cylindrical bearing race and the end portion.
In accordance with another embodiment, a motorized actuator includes a housing, an intermediate gear assembly, and first and second play reduction assemblies. The intermediate gear assembly is mounted in the housing for rotation about an axis. The intermediate gear assembly includes a shaft, a driving gear, and a driven gear. The shaft has opposite first and second end portions. The driving gear is engaged to the shaft, and is axially disposed between the opposite first and second end portions. The driven gear is engaged to the shaft, and is axially disposed between the driving gear and one of the second end portion. The first and second play reduction assemblies are mounted to the respective first and second end portions, and are seated to the housing. The first and second play reduction assemblies each include a stop shim adapted to axially abut the first and second end portions, respectively, and a needle bearing adapted to rotationally support the shaft.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring now to the Figures, where the invention will be described with reference to specific embodiments, without limiting same, an actuator 20, which may be motorized, is illustrated in
The actuator 20 may include a gear train 22, an electric motor 24, a controller 26 (e.g., electronic circuit board), an electrical connector 28, and a housing 30. The electrical connector 28 may facilitate the communication of control signals to the controller 26, and the routing of electric power to the controller 26 and the motor 24. In operation, the motor 24 is adapted to drive the gear train 22 within the housing, and the gear train drives the application (i.e., throttle plates, EGR valves, etc.).
In one embodiment, the gear train 22 includes an input shaft 32 (i.e., motor rotor), an intermediate shaft 34, an output shaft 36, an input gear 38, at least one intermediate gear (i.e., two illustrated as 40, 42), and an output gear 44. The input shaft 32 is adapted to rotate about a motor axis 46, the intermediate shaft 34 is adapted to rotate about an axis 48, and the output shaft 36 is adapted to rotate about an axis 50. The axes 46, 48, 50 are spaced from, and substantially parallel to, one-another. In other embodiments, additional gears may be part of the gear train 22 and mounted for rotation within the housing 30. Moreover, gear architecture may facilitate the axes 46, 48, 50 not being parallel to one-another in order to meet a packaging requirements and/or the needs of a specific application.
The gears 38, 40, 42, 44 may each include a plurality of gear teeth (not shown) for coupling with the teeth of adjacent gears as is known by one having skill in the art. Gear 38 is centered and fixed to an end portion of input shaft 32, gears 40, 42 are centered and fixed to a mid-portion 52 of intermediate shaft 34 (see
In one embodiment, actuator 20 may further include a lip seal 54 seated to the housing 30, and adapted to seal about the rotating output shaft 36. Various bearings 56 may also be seated within, and to, the housing 30 for supporting and facilitating relatively friction free rotation of the output shaft 36.
Referring to
In one embodiment, the housing 30 includes two housing segments 72, 74 adapted to be fastened together during assembly. The first housing segment 72 includes a cylindrical surface 76 and an end face 78 that may be circular. The cylindrical surface 76 and the end face 78 define the boundaries of a blind bore 80 in the housing segment 72. The second housing segment 74 includes a cylindrical surface 82 and an end face 84 that may be circular. The cylindrical surface 82 and the end face 84 define the boundaries of a blind bore 86 in the housing segment 74.
When the actuator 20 is fully assembled, the end portions 68, 70 of the intermediate shaft 34 and the respective bearing assemblies 60, 62 are disposed in the respective blind bores 80, 86. More specifically, the needle bearings 64 of the bearing assemblies 60, 62 are seated against the respective cylindrical surfaces 76, 82, and the stop shims 66 of the bearing assemblies 60, 62 are placed against the respective end faces 78, 84. The intermediate shaft 34 is not constrained axially by needle bearings 64, and is thus capable of moving axially within the needle bearings.
In one embodiment, the stop shims 66 are disc-shaped each having a cylindrical side 88 that opposes, and is press fitted or close proximity to, the respective cylindrical surfaces 76, 82 carried by the respective housing segments 72, 74. The stop shims 66 are adapted to limit axial displacement of the intermediate shaft 34, and are made of a material that is harder than the material of the housing 30. For example, the stop shims 66 may be metallic while the housing may be made of a softer material (e.g., plastic). In another embodiment, the stop shims 66 may be made of steel and the housing 30 may be made of cast aluminum. To minimize friction, between the rotating intermediate shaft 34 and the stop shims 66, the shims may be coated with a friction reducing material such as graphite, Teflon, or others. In another embodiment, the stop shims may be a unitary part of the housing, or the housing may be made, at least partially, of a hardened material such that separate stop shims are not needed.
In one example, the axial displacement of the intermediate shaft 34 may be limited to a minimum displacement of greater than about 0.111 millimeters and a maximum axial displacement of about 0.289 millimeters (i.e., the maximum axial play). In one example, a diameter (see arrow 90 in
Referring to
Advantage and benefits of the present disclosure include an intermediate shaft whose axial displacement is not constrained by bearings, and is thus allowed to freely move axially for improved distribution of axial forces. Other advantages include an alternative to the use of ball bearings that may break during axial loading. Yet further, the present disclosure provide a relatively simple, robust, and optimized packaging design.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.
