Patent Application
20100284835
This disclosure relates to a modified pump gear for handling the expected stresses within a pump assembly of a generator.
Electrical generators typically include a shaft that is driven for rotation and which carries a plurality of field coils or permanent magnets. The generator may be used to also drive a hydraulic pump, such as for cooling the generator or other components of a system. A gear train may be used between the generator and the hydraulic pump. Misalignment of the gears within the gear train relative to the shafts, bearings, or other components, may increase wear on the gears and contribute to a reduction in gear durability. For instance, axial misalignment of the gears may cause uneven wear of the gear teeth and eventually necessitate replacement.
An exemplary pump gear includes a pump gear body having involute teeth that each have an involute surface that extends between a tooth tip and a tooth base. The involute surface includes at least reference points A-D, with reference point A near the base, reference point D near the tip, reference point B between reference points A and D, and reference point C between reference points B and D. The reference points A-D have associated respective roll angles, εA-D, between a corresponding first line that is perpendicular to the involute surface at the given reference point A-D, and a second line that is tangent at a reference point that lies on a terminal end of the involute surface at the tooth base to a reference base circle having a center origin at the center axis.
In embodiments, the pump gear may be part of a pump assembly for a generator, with the pump gear mounted on a pump shaft that is rotatable about a central axis.
In embodiments, the pump gear may be part of a generator and may be mounted on a pump shaft within a pump that is operatively coupled to a rotor shaft of the generator through a gear train. The gear train may include a rotor gear mounted on the rotor shaft, an idler gear engaged with the rotor gear, and the pump gear, which is driven by the rotor gear through the idler gear. A rotor is mounted on the rotor shaft within a stator having a plurality of magnetic members circumferentially spaced around the rotor shaft.
An exemplary method for processing a pump gear for a generator may include forming the pump gear body and establishing the roll angle εA to be 11.96°-13.96°, the roll angle εB to be 14.79°-16.79°, the roll angle εC to be 23.29°-25.29°, and the roll angle εD to be 26.12°-28.12°.
The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
In the illustrated example, the generator 10 includes a dynamoelectric portion 20, a hydraulic pump 22, and an idler gear 48 between the hydraulic pump 22 and the dynamoelectric portion 20. The dynamoelectric portion 20 includes a rotor shaft 25 that is rotatable about a central axis 26. A rotor 28 is mounted on the rotor shaft 25 to be driven about the central axis 26 within a stator 30 (shown in part). The rotor 28 includes a plurality of magnetic members 32, such as field coils or permanent magnets, circumferentially spaced about the rotor 28 relative to the central axis 26. The general arrangement of dynamoelectric machines is known and may vary from that shown in the illustrated examples.
The generator 10 includes a gear train 40 for driving the hydraulic pump 22 via the dynamoelectric portion 20. In this case, the gear train 40 is a gear reduction train to drive the hydraulic pump 22 at a relatively slower speed than the dynamoelectric portion 20. However, the gear train 40 may be modified in other examples.
The hydraulic pump 22 includes a pump gear 44 mounted for rotation on a pump shaft 46. In this case, the pump gear is mounted with a fastener 52 that extends axially, relative to a central axis 54 of a pump shaft 46, through the pump gear 44 into the pump shaft 46. The remainder 56 of the hydraulic pump 22 is a known arrangement and may include journal bearings 56a for rotatably supporting the pump shaft 46, a liner sleeve 56b, a wear plate 56c between the journal bearings 56a and liner sleeve 56b, and one or more vanes 56d that are rotatable with the pump shaft 46 for moving a fluid, for example.
The gear train 40 includes a rotor gear 42 mounted on the rotor shaft 25, the pump gear 44 mounted on the pump shaft 46 of the hydraulic pump 22, and an idler gear 48 mounted for rotation on journal bearings 50a and 50b. In this case, the dimensions of the journal bearings 50a and 50b may vary from part to part through normal manufacturing processes, design tolerances, or both such that there is possible axial and radial position variation of the idler gear 48 depending on the particular dimensions of the journal bearings 50a and 50b. However, as will be described, the exemplary pump gear 44 and pump shaft 46 are configured to facilitate reducing any effects from the dimensional variations of the journal bearings 50a and 50b.
For instance, to increase the life of the pump gear 44 by increasing durability, the pump gear 44 includes teeth 60 (
Each involute surface 64 may terminate on a radially outer end at the tip 66 and at a radially inner end at a point 72 near the base 68. For instance, the point 72 may represent the point at which the involute surface 64 inflects to form a valley between neighboring teeth 60.
In profile, the involute surface 64 includes at least reference points A-D thereon, with reference point A near the base 68, reference point B near the tip 66, reference point B between reference points A and D, and reference point C being between reference points B and D. In embodiments, reference point A may essentially be at the point 72 of the terminal end of the involute surface 64 and reference point D may essentially be at the radially outer terminal end of the involute surface 64. In some examples, the locations of reference points B and C may be a function of a distance between reference points A and D. In one example, reference point B is located 20% of the distance (from reference point A), and reference point C is located 80% of the distance (from reference point A).
Each of the reference points A-D includes an associated roll angle, εA-D, between a corresponding first line 80A-D and a second line 82 that is tangent at the point 72 to a reference base circle 83 having a center origin at the center axis 62. For instance, the roll angles εA-D are subtended by a portion of the involute surface 64. The locations of the reference points A-D and the magnitudes of the roll angles εA-D may be determined using a known involute-checking machine.
The following examples suppose that reference point A is at the point 72 of the terminal end of the involute surface 64, reference point D is at the radially outer terminal end of the involute surface 64, reference point B is located 20% of the distance (from reference point A), and reference point C is located 80% of the distance (from reference point A). In one example, the roll angle εA is 11.96°-13.96°, the roll angle εB is 14.79°-16.79°, the roll angle εC is 23.29°-25.29°, and the roll angle εD is 26.12°-28.12°.
Utilizing roll angles εA-D within the given ranges provides a profile of the involute surface 64 that accommodates the expected specific loads on the pump gear 44 for the expected rotational speeds of the generator 10. That is, the radian measures of the given roll angles εA-D are the tangents of the pressure angles at the points on the involute surface 64 and are designed through the given roll angles εA-D to accommodate a particular stress state on the teeth 60.
In further examples, the roll angle εA is 12.46°-13.46°, the roll angle εB is 15.29°-16.29°, the roll angle εC is 23.79°-24.79°, and the εD is 26.62°-27.62°. In a further example, the roll angle εA is 12.96°, the roll angle εB is 15.79°, the roll angle εC is 24.29°, and the roll angle εD is 27.12°.
Referring to
The central opening 94 may be non-circular (see
The wall 96 includes a shoulder 100a (e.g., a step) for locating the pump gear 44 on the pump shaft 46. Likewise, the pump shaft 46 may include a corresponding shoulder 102 (
As an example, the shoulder 100a is located a predetermined distance from the axial face 98a. In embodiments, an axial distance 104a between the axial face 98a and the shoulder 100a may be 0.270±0.003 inches (0.686±0.008 centimeters). An axial distance 104b from the axial face 98a to the nearest side of the involute teeth 60 may be 0.173±0.005 inches (0.439±0.013 millimeters). The distances from the shoulder 100a to the axial face 98a and shoulder 100a to the involute teeth 60 determine the axial position of the pump gear 44 for axial alignment with the idler gear 48. Thus, upon assembly of the generator 10, the pump gear 44 will be at a fixed position and aligned with the idler gear 48 such that any variation in the position of the idler gear 48 causes minimal misalignment with the pump gear 44.
In the illustrated example, the pump gear 44 may also include another shoulder 100b that is adjacent to the first shoulder 100a. In this regard, the shoulders 100a and 100b form two steps (i.e., a double shoulder). When the pump shaft 46 is inserted into the opening 94 of the pump gear 44, the end of the pump shaft 46 abuts the axial face of the shoulder 100a. The second shoulder 100b provides a clearance between the end of the pump shaft 46 and the remaining portion of the opening 94 such that the pump shaft 46 does not bottom out on another component that is adjacent to the pump gear 44.
Additionally, the pump gear 44 may include an undercut 106 that is immediately adjacent to the first shoulder 100a. In this case, the undercut 106 is on the side of the shoulder 100a that will receive the pump shaft 46. The undercut is recessed from the portion of the wall 96 to the left in the
The spokes 124 provide strength and structural rigidity to the pump gear 44. In this case, the absence of any material in the openings 126 also reduces the overall weight of the pump gear 44 and thus the overall weight of the generator 10.
The pump gear 44 may be formed with the desired roll angles in a known gear manufacturing process. For instance, the process may include casting, forging, powder metallurgy, and/or machining from a blank. Thus, the process for forming the pump gear 44 is not limited to any particular type as long as the selected process is capable of establishing the roll angles to be within the given example ranges.
Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.
