FACE COMMUTATOR WITH A PRESS-FITTING HUB

Abstract: Face commutators (30) with substantially planar commutating segments (31) that are bonded to a conductive member (33) which is attached to an insulating hub (41). The hub (41) has an axial bore (43) designed to be press-fitted on the armature shaft (23) of a motor with an inner wall section (43) that is deformed by the motor shaft (23). The hub (41) is configured with an inner wall section that has contact sections (46) and relieft sections (47), wherein the contact sections are closer to the central axis of the hub than the radius of the shaft and which are deformed when the hub is pressed on the shaft. While the relief sections (47), which do not come in contact with the shaft, allow the commutator to adapt to the shaft and provide room for material that is displaced from the contact sections. The hub (41) and, to a limited extent, the metallic conductive elements (33), absord any stresses and deformation from press-fitting the hub onto the motor shaft without transmitting undue stress and deformation to the interface betweenthe conductive elements and the carbon communtating segments (31).

Description: Face Commutator with a Press-Fitting Hub Field of the Invention This invention relates to face commutators, i.e., commutators with a number of commutating elements arranged in a face or plane that is substantially normal to the axis of rotation of the commutator. More particularly, it relates to face commutators that can be manufactured economically and efficiently, that can be securely mounted on a motor shaft without requiring any special machining or dimentioning of the motor shaft, and that provide reliable, dependable operation. Background of the Invention Carbon faced commutators, i.e., face commutators in which generally pie-shaped commutating elements are arranged in a planar face at a right angle to an armature shaft, are frequently used for demanding applications such as fuel pumps designed to be immersed in a fuel tank that may hold mixtures with methanol, ethanol or other fuels with relatively high levels of oxygen moities. The carbon commutating elements are substantially more durable in this type of environment than copper or other metallic conductors. And the face arrangement saves space and contributes to a compact design. For these applications, which are intended to operate for extended periods of time, preferably for the life of the vehicle, simple compact motors which are durable yet economical to produce are highly desirable. Commutators for these applications are disclosed in various patents, including U.S. 5,552,652 to Shimoyama et al, which illustrates a design in which carbon segments are surrounded on three sides by an insulating hub; U.S. 5,793,140 to Tuckey and U.S. 5,925,962 and U.S. 5,962,946 to Kobman et al, disclosing a design with conductive metallic elements embedded in the carbon face segments and extending through the rear of the carbon face segments into a molded insulating hub; and U.S. patents 5,386,167; 5,442,849 and 5,667,588 to Strobl, which disclose designs in which the carbon face segments extend through metallic conductors and into or through the insulating hub. All of these commutators are designed to offer durability. Unfortunately, they all add complexity and increase the cost of producing the commutator. Thus, they are generally less desirable than the designs disclosed in U.S. patents 5,175,463; 5,255,426 and Re 36,248 to Farago et al; U.S. 5,157,299 to Gerlach; U.S. 5,245,240 to Takasaki and U.S. 5,400,496 to Kemmner et al, all of which show designs in which substantially flat carbon face segments are soldered or otherwise bonded to metallic conductors which are attached to an insulating hub. These designs simplify production of elements of the commutator. Commutators have normally been mounted on armature shafts with splines, knurling or other projections to secure the commutator in place. However, armature designs are now being developed which can be mounted on a simple cylindrical armature shaft. It would be desirable to have commutators that could be mounted in a similar manner. U.S. patent 4,760,301 to lizima et al discloses a cylindrical or barrel commutator with copper commutating elements on the outer cylindrical surface and an insulating hub, that is designed to be press-fit on a cylindrical shaft. However, the hub of the commutator is deformed significantly in this process. This amount of deformation would not be acceptable in the carbon face commutators disclosed by Farago et al, Gerlock, Takasaki, and Kemmner et al Summary of the Invention This invention provides face commutators with substantially planar commutating segments, bonded to a conductive member which is attached to an insulating hub. The hub has an axial bore designed to be press fit on the armature shaft of the motor. The axial bore has an inner wall section that is deformed by the motor shaft. The inner wall has contact sections that are closer to the central axis of the hub than the radius of the shaft, and which are deformed when the hub is pressed on the shaft, and relief sections that are further from the central axis of the hub than the radius of the shaft. These relief sections, which do not come in contact with the shaft, allow the commutator to adapt to the shaft and provide room for material that is displaced from the contact sections. The hub and, to a limited extent, the metallic conductive elements, absorb any stresses and deformation from press-fitting the hub onto the motor shaft without transmitting undue stress and deformation to the interface between the conductive elements and the carbon commutating segments. Thus, this invention provides the advantages of simple, planar segments with the advantages of a press-fitting hub. Other features, advantages and objectives of this invention will be apparent from the following detailed descriptions. Drawings Figure 1 is a partially sectioned view of a fuel pump embodying this invention. Figure 2 is a plan view of a commutator embodying this invention. Figure 3 is a cross-sectional elevation view along lines 3-3 of Figure 2. Figure 4 is an enlarged view of the central bore of the hub in Figures 2 and 3. Figures 5 and 6 are enlarged plan views of other hubs that may be used for commutators embodying this invention. Detailed Description The fuel pump module illustrated in Figure 1 is designed to operate in the fuel tank of a motor vehicle. As noted above, these systems must be capable of reliable operation for long periods of time. Economy is also desireable. The illustrated system has a fuel pump 10 which is mounted on one end of and driven by a motor, generally referred to as 20. The fuel pump and motor, mounted within a case 11, draw fuel in tlirough an inlet filter 15 at one end of the case and pump the fuel through the case and out through a discharge outlet 17 at the other end of the case. The motor has an armature 21 mounted on a armature shaft 23, and a permanent magnet stator 25. The armatator shaft also extends through a commutator, generally referred to as 30, at one end of the armature. Brushes 27, 28 supply current to the commutator 30, which is connected to windings of the armature. Commutator 30, which is illustrated in Figures 2-4, has eight carbon face segments 31 equally spaced about the end or face of the commutator. Other embodiments may have more face segments, or less. The carbon faced segments are soldered or otherwise bonded to conductive segments 33, typically of copper, which are attached to an insulating hub 41. Tangs 35 extend laterally from each conductive segment, as illustrated in Figure 2 and 3, to provide electrical connections to the armature windings. As seen in Figure 3, anchoring tabs 37, 39 extend from the bottom of the conductive segments into the insulating hub. Slits 38 separate and insulate the individual carbon face segments and conductive segments from adjacent segments. The commutator is produced by molding the insulating hub 41 to a sheet of copper or other conductive material, which has partially formed tangs extending radially or laterally outward and anchoring tabs formed into the position shown in Figure 3. A carbon ring with flat or planar surfaces, as illustrated in Figure 3, is then bonded to the sheet of conductive material, preferably by soldering, using solder rings of conventional solder compositions. The slits are then cut tlirough the carbon ring, through the solder 32, through the conductive sheet and slightly into the insulating hub, to insulate the individual commutating segments from each other, and the tangs 35 are formed into the final shape illustrated in Figure 3. In the process of molding the insulating hub 41 to the pre-form for the conductive segments, an axial bore 43 for the armature shaft is molded into the hub. The axial bore illustrated in Figure 4 has eight flat or planar sides 44 that meet each other, forming a polygon. Central sections of the sides of the polygon act as contact sections 46 which are contacted and deformed by the armature shaft when the commutator is press-fit onto the shaft. Outer sections of the sides, which meet to form corners of the polygon, act as relief sections 47. The relief sections do not contact the armature shaft, and provide space for displacement of phenolic material during the press-fitting operation. Figures 5 and 6 illustrate alternative press-fit hubs embodying this invention. The hub in Figure 5 is similar to the hub in Figure 4, except that the axial bore 53 illustrated in Figure 5 has eight flat or planar sides 54 alternating with eight arcuate segments 55. The arcuate sections cover an arc of about 15° and the flat or planar sides span an arc of about 30°. The centers of the flat sides, which are closer to the central axis of the hub than the radius of the armature shaft, act as contact sections 56 which are contacted and deformed by the armature shaft. The arcuate sections and the outer ends of adjacent flat walled sections, which are further from the central axis of the hub than the radius of the shaft, act as relief sections 57. The press-fit hub illustrated in Figure 6 comprises a serpentine wall 63 with inner section 66, closer to the hub of the commutator than the radius of the armature shaft, that function as contact sections, and outer sections 67, further from the hub of the commutator than the radius of the commutator, that function as relief sections. Those skilled in the art of commutator design and application will readily appreciate other advantages they can obtain through the use of the designs described above. They will also appreciate that the specific systems described herein are merely illustrative. Many modifications can be made these systems within the scope of this invention, which is defined by the following claims.

Claims: We claim: 1. A face commutator comprising: an insulating hub having an axial bore; conductive elements attached to said insulating hub; carbon commutating segments bonded to said conductive elements and defining a planer face; said axial bore being designed and adapted for press-fitting onto a shaft of an electric motor and comprising an inner wall section that is and is deformed by said motor shaft; and said inner wall comprising contact sections that are closer to the central axis of said hub than the radius of said shaft and relief sections that are further from said central axis than said radius. 2. A face commutator according to claim 1 wherein said contact sections alternate with said relief sections around the periphery of said axial bore. 3. A face commutator according to claim 2 wherein said inner wall section comprises a polygon, said contact sections comprise central sections of sides of said polygon and said relief sections comprise outer sections of said sides of said polygon. 4. A face commutator according to claim 2 wherein said inner wall section comprises substantially flat wall sections and arcuate cylindrical sections, said contact sections comprise central sections of said flat wall; and said relief sections comprise said arcuate cylindrical sections and outer ends of adjacent flat wall sections. 5. A face commutator according to claim 2 wherein said inner wall comprising a serpentine edge with inner sections that are closer to the center of said axial bore than the radius of said motor shaft, and outer sections that are further from the central axis of said bore than the radius of said motor shaft. 6. A face commutator according to claim 1 wherein said commutator segments comprise segments of a cylinder having a substantially planar top and a substantially planar bottom. 7. A face commutator according to claim 6 wherein said conductive elements comprise sections of a substantially planar metallic plate. 8. A face commutator according to claim 7 wherein said conductive elements further comprise anchor tabs extending into said insulating hub. 9. A face commutator according to claim 7 which is produced by attaching said metallic plate to said insulating hub, bonding a toroidal carbon ring to said metallic plate, and slitting said carbon ring and said metallic plate to form said commutating segments and said conductive segments. 10. A face commutator according to claim 9 wherein said toroidal carbon ring is soldered to said metallic plate. 11. An electric motor comprising an armature shaft having an armature and a face commutator mounted on said armature, said commutator comprising: an insulating hub having an axial bore; conductive elements attached to said insulating hub; and carbon commutating segments bonded to said conductive elements and defining a planer face; said axial bore being designed and adapted for press-fitting onto a shaft of an electric motor and comprising an inner wall section that is and is deformed by said motor shaft; said inner wall comprising contact sections that are closer to the central axis of said hub than the radius of said shaft and relief sections that are further from said central axis than said radius.

Inventors: CEFO NEVRES, CEFO, NEVRES
Applicants: CEFO NEVRES, KIRKWOOD IND INC, CEFO, NEVRES, KIRKWOOD INDUSTRIES, INC.
Application year: 2000
Main classification: H02K13
IPC codes: H01R39, H02K5, H02K13