Abstract
A contaminant-resistant motor may include an endbell with hermetic sealing of control components within a control module cavity in the endbell. The endbell configuration includes a front wall that isolates the control module cavity from contaminant-prone area of the motor assembly. The stator leads may be sealed within the lead passages using glass or other seals to further isolate the stator leads and control module cavity against ingress of contaminating liquids from the motor interior. The endbell configuration permits larger bearing elements to be used. A method of assembly of the motor may involve first fixture to align the stator, housing and REB to ensure concentric alignment of the stator to housing and the REB to the housing and a second fixture to isolate front and rear bearing bores and the stator inner diameter from encapsulation material and permit the stator to be molded to the housing.
Claims
1. A contaminant-resistant motor for surgical applications comprising: a housing including a housing wall defining a housing interior; a front endbell; a rear endbell, the rear endbell defining a control module cavity; a stator; a rotor; a control module within the rear end bell, wherein the control module is hermetically sealed within the control module cavity and isolated from the housing interior.
2. The motor of claim 1, further comprising at least one stator lead extending from the control module, the at least one stator lead being sealed against contaminants at least partially by encapsulation within the control module cavity.
3. The motor of claim 2, wherein the at least one stator lead includes a stator lead having an exterior section that extends outside of control module cavity and wherein the stator lead exterior section extends through a seal for sealing the stator lead exterior section from contaminants.
4. The motor of claim 3, wherein the seal is a glass seal.
5. The motor of claim 1, wherein the control module is hermetically sealed by encapsulation.
6. The motor of claim 5, further comprising at least one sensor in electrical communication with the control module, the at least one sensor being hermetically sealed by encapsulation in the control module cavity with the control module.
7. The motor of claim 5, wherein the stator is encapsulated to an interior surface of the housing cavity.
8. The motor of claim 1, further comprising a bearing pocket formed in a front portion of the housing, wherein the stator has an inner diameter that is smaller than the diameter of the bearing pocket.
9. The motor of claim 1, further comprising at least one Hall magnet on the motor shaft that is hermetically isolated from the control module cavity.
10. The motor of claim 1, further comprising a rear bearing disposed within the rear endbell, and at least one motor rotation sensor located rearward of the rear bearing.
11. The motor of claim 1, wherein the rear endbell has an exterior surface that is continuous with an exterior surface of the housing.
12. The motor of claim 1, wherein the rear endbell includes a shoulder formed therein for engaging a wall of the housing.
13. A method of making a motor for a surgical device comprising: providing a motor housing having a housing wall and an integrally formed front end bell; securing a stator within the housing; securing a rear endbell to the housing; encapsulating the stator to the housing; and placing a rotor within the stator.
14. The method of claim 13, further comprising the step of providing a control module with conductors in the rear end bell and the step of encapsulating the control module and conductors within the rear endbell.
15. The method of claim 13, further comprising the step of orienting sensors in the rear endbell relative to the stator and the step of encapsulating sensors in the rear endbell.
16. The method of claim 13, further comprising the step of providing a rear bearing and providing sensors in a location that is rearward of the rear bearing.
17. The method of claim 13, further comprising the step of aligning a fixture within the housing to align the stator, housing and rear endbell, and the step of utilizing the fixture in an encapsulation step.
18. The method of claim 13, further comprising the step of encapsulating commutation magnets, sensors, bearings and a control module in an encapsulation operation.
Description
DESCRIPTION OF THE DRAWINGS
[0017] The above and other attendant advantages and features of the invention will be apparent from the following detailed description together with the accompanying drawings, in which like reference numerals represent like elements throughout. It will be understood that the description and embodiments are intended as illustrative examples and are not intended to be limiting to the scope of invention, which is set forth in the claims appended hereto.
[0018] FIG. 1 is cross-section of a prior art motor configuration as discussed above.
[0019] FIG. 2 is a cross-section of an example motor configuration according to an aspect of the disclosure.
[0020] FIG. 3 is a cross-section of details of the example motor configuration of FIG. 2.
[0021] FIG. 4 is an exploded perspective view of an example motor configuration according to an aspect of the disclosure.
[0022] FIG. 5 is detailed front perspective view of an example motor rear endbell according to an aspect of the disclosure.
[0023] FIG. 6 is a detailed rear perspective view of an example motor rear endbell according to an aspect of the disclosure.
[0024] FIG. 7 is detailed front perspective view of an example endbell control module cavity encapsulation according to an aspect of the disclosure.
[0025] FIG. 8 is a sectional view of an example endbell and encapsulation according to an aspect of the disclosure.
[0026] FIG. 9 is a cross-section of an example assembled motor according to an aspect of the disclosure.
[0027] FIG. 10 is a cross-section of an example alignment pin used in a motor assembly process according to an aspect of the disclosure.
[0028] FIG. 11 is a cross-section of an example pin used in a motor assembly process according to an aspect of the disclosure.
DETAILED DESCRIPTION
[0029] FIGS. 2 and 3 are cross-sections of an example motor assembly 100 according to an aspect of the disclosure. The motor assembly 100 includes primary components of a generally cylindrical motor housing 110 with an integrated front endbell 113. A stator assembly 120 is secured within the housing 110 in a manner which will be described below. A rear bearing 116 and commutation magnets 112 are disposed within the housing in cooperative relationship with a rear endbell 130. Rear endbell 130 defines a control module cavity 132, which houses a PCB 180, as well as sensors 118 (one shown in FIG. 2), sensor leads 119 connecting sensors 118, which may be Hall effect sensors, to PCB 180, and external leads 124. At least one PCB to stator lead 122 extends from the PCB 180 thru a glass seal 126 situated in a front wall of the endbell 130 and further to elements of the stator assembly 120. The control module cavity 132 is filled with an encapsulation material 190, which seals and secures the components housed therewithin.
[0030] FIG. 4 is an exploded view showing the general assembly of the primary components of an example motor assembly 100 according to an aspect of the disclosure. Housing 110 contains an encapsulation 115, which surrounds a stator frame 121 for supporting stator elements 120. A rotor 150 is secured within front bearing 114 and rear bearing 116 secured within the motor assembly. Rear endbell 130 is secured to an end of the housing 110 and includes encapsulation 190 within the control module cavity of endbell 130.
[0031] FIGS. 5 and 6 are perspective views illustrating details of an example rear endbell 130 according to an aspect of the disclosure. The endbell 130 may have a unitary construction and be machined from a single piece of stainless steel, for example. Endbell 130 may include an outer wall 133 and a front wall 134 which defines a control module cavity 132 on a rear side thereof. According to an aspect of the disclosure, front wall is solid, except for stator lead passages 136. Stator lead passage 136 receive stator leads, which are sealed, as will be later explained. Thus, the control module cavity 132 remains isolated from the front of the motor, including areas that may be prone to ingress of contaminating liquids. A rotor end cap 138 may be formed/machined integrally in the front wall 134 for receiving an end of the rotor and housing commutation magnets, as well as permitting advantageous orientation of sensors within the control module cavity, as will be explained.
[0032] Referring to FIG. 6, outer wall 133 may include a recessed or thinned portion 139 in relation to the stator lead passages 136, which may be oriented in a circumferential pattern near the perimeter of front wall 134. The recessed or thinned portion 139 of the outer wall 133 is advantageous in permitting location of the stator leads in a manner that maximizes the available space within the control module cavity 132 for other components. More particularly, the orientation and spacing of the stator leads is optimized to provide mechanical and electrical clearance inside the end bell encapsulation, as well as to mitigate electronic interference with other components. These features also provide advantages in assembly of the motor and for improved sealing and encapsulation of the stator leads within the control module cavity.
[0033] Endbell 130 may also include an integral forward annular wall which provides a bearing housing 140, which, in combination with the rotor receiving end cap 138 provides for very accurate relative orientation of the commutation magnets and sensors with respect to the rotor and rotor end. Endbell 130 may also include a forward annular housing engaging shoulder 142 for flush mounting of the endbell 130 on housing 110 (FIG. 4). Endbell 130 may be fastened and sealed to the housing by laser welding or other suitable fastening techniques. The rear end of the endbell 130 may include a rear annular shoulder 144 to center endbell 130 to housing 110. An interior circumferential slot 146 provides additional sealing of the encapsulation and secures the encapsulation against axial movement within the control module cavity 132.
[0034] FIG. 7 is a perspective view of an example encapsulation 190 (with endbell omitted) according to an aspect of the disclosure. As will be recognized, the recessed or thinned portion of the endbell annular wall (139 in FIGS. 5 and 6) results in an extended portion 192 of the encapsulation 190 in which the stator leads 122 are advantageously sealed, secured and oriented near the perimeter of the encapsulation. Seals 126, which may be glass seals, and which are disposed in the stator lead passages (not shown in FIG. 7) further isolate the portions of the stator leads that extend beyond the endbell front wall to the stator elements. With this configuration, the stator leads are completely isolated from the areas of the motor which are prone to contamination by ingress of liquid. Encapsulation 190 may include a retaining ridge 194 formed during encapsulation as encapsulation material flows into the interior circumferential slot 146 (FIG. 4).
[0035] FIG. 8 is a cross-section illustrating an example rear endbell with encapsulation of components in the control module cavity. PCB 180 may be provided with ports 182 for permitting encapsulation material to flow therethrough during a encapsulation process, further securing the PCB 180 in position. Again, as can be seen in this illustration, the PCB 180 and the components thereon, including the sensors 118 may be precisely located relative to the integral rotor end cap 138, and therefore the rotor shaft during an encapsulation step. More particularly, the components may be precisely located on the PCB during a PCB manufacturing step. Then, during motor assembly, the orientation of the PCB and components thereon, including sensors 118 may be precisely controlled by the positioning of the stator leads within the seals and stator lead passages 136. This includes tuning the endbell 130 to housing 110 before encapsulation. This may position the Hall sensors precisely with regard to the stator before encapsulation.
[0036] FIG. 9 is a cross-section of an example assembled motor according to an aspect of the disclosure.
[0037] According to another aspect of the disclosure, the stator elements may be encapsulated into the housing. The encapsulated stator inner diameter—“S” in FIG. 9—is advantageously encapsulated smaller than the diameter of the bearing pocket provided in the front of the housing 110—“B” in FIG. 9. This allows an encapsulation tool, such as a core pin, to create a blind opening, and creating hermetic isolation of Hall magnets (in the front partition of the motor) from the sensors 118, i.e., Hall sensors (in the back partition of the motor). Another advantage is that the larger pocket for the front bearing permits a larger, more durable bearing to be used. In addition, a fixture may be used as part of the encapsulation tooling, to critically align the stator, housing and rear endbell. Such alignment is necessary for precise control and shut-off of the encapsulation material during encapsulation. The fixture may align the core pin with respect to the bearing bore in the endbell. The fixture aligns the front bearing bore of the housing. Finally, the fixture minimizes the potential for runout (affects high speed performance) between the two bearing bores and permits the use of a smaller nominal gap between the stator and the rotor because of the precise alignment provided by the fixture positioning and reduction in the number of components in the tolerance stack-up.
[0038] According to an example process for motor assembly, the following steps may be undertaken. First, pins 122 (FIG. 8) may be sealed in glass seals within the stator lead passages 136 (FIG. 8) in the endbell 130. Next, the PCB with hall sensors thereon may be assembled over the pins 122 and soldered and bonded in place. This assembly is then encapsulated within the endbell control module cavity. The stator leads are then soldered to the glass pins on the opposite side and the endbell is assembled to the housing 110. Referring to FIG. 10, a first fixture in the form of an alignment pin 200 may be used to align the housing, rear endbell and stator assembly. The alignment pin 200 may have a first end that fits within the rear endbell bearing bore 140 and also has portions that engage the interior diameter of the stator 120 and the housing bearing bore 115 such that these components are held in precise alignment. The motor may be tuned by rotation of the endbell 130 relative to the housing such that the sensors are in a correct orientation to properly control current in the stator elements. Once proper alignment of the rear endbell bearing bore 140, stator interior diameter, and housing bearing bore 115 is achieved, the endbell 130 is fastened to the housing by welding or other fastening techniques. The stator is also fastened in place by bonding to the housing interior using adhesive or other bonding material. A motor-side encapsulation space 210 may be defined in front of the rear endbell 130. Referring additionally to FIG. 11, assembly may also include an encapsulation step to encapsulate the motor side of the rear end bell as well as other internal areas of the motor that require sealing. A pin 300 may be inserted into the housing/stator/endbell assembly and may isolate the housing and rear endbell bearing bores, as well as the stator inside diameter, from encapsulant. Encapsulant may be introduced via one or more ports defined in the housing wall and may flow into encapsulation space 210, further sealing and isolating the components, namely the stator leads and any contaminant migration paths, on the motor side of the rear endbell 130. Following the encapsulation step, the pin 300 may be removed and the motor bearings, rotor and seals installed. As will be recognized, that aforedescribed process provides improved encapsulation and sealing of the components within and adjacent the rear end bell and isolates the control components from contaminants
[0039] It should be understood that implementation of other variations and modifications of the invention in its various aspects may be readily apparent to those of ordinary skill in the art, and that the invention is not limited by the specific embodiments described herein. It is therefore contemplated to cover, by the present invention any and all modifications, variations or equivalents.
