Patent Application
20190264588
This disclosure relates to the field of transmission systems. More particularly, the disclosure pertains to a transmission utilizing an adapter to control the spacing between a sump bottom and a pump inlet.
Automatic transmission fluid serves many functions in a modern automatic transmission. Pressurized fluid may be used to engage friction clutches in order to establish a power flow path with a desired speed ratio. Fluid lubricates gears and bearings. Excess heat is removed by fluid flowing over various components. When the fluid contains contaminants, it may be less effective in these functions and may cause failures such as stuck valves. Therefore, transmissions often include fluid filters. The fluid typically drains to a sump due to gravity. A transmission pump draws fluid from the sump and delivers pressurized fluid to a valve body, which distributes the fluid to various places within the transmission at pressures appropriate to the various functions.
A transmission includes first and second housings, a pump assembly, and an adapter. The pump assembly is supported by the first housing. The pump assembly may include a suction filter. The pump assembly has an inlet separated from an interior surface of the second housing by a distance. The adapter includes a deformable bellows and a fin. The bellows connects the inlet to the fin. The adapter has a free length, measured between the inlet and a tip of the fin, that is greater than the distance. The fin is chamfered on an edge opposite the first housing. The first and second housings may define a sump filled with fluid such that deformable bellows penetrates a surface of the fluid, placing the bellows inlet below the fluid surface.
A method of assembling a transmission includes attaching a pump to a first transmission case half, attaching a bellows to an inlet of the pump, and bringing the first transmission case half together with a second transmission case half. Attaching the bellows to the pump inlet may include attaching a filter between the pump inlet and the bellows. An end of the bellows opposite the inlet is fixed to a fin. As the transmission case halves are brought together, the second case half rubs against a chamfered edge of the fin to compress the bellows. The case halves may be sealed to one another to define a sump, which is then filled with fluid.
A transmission suction filter adapter includes a deformable bellows and a chamfered fin. The bellows has a top lip and a bottom lip. The top lip is configured to seal against a suction filter inlet. The bottom lip is fixed to the chamfered fin. The chamfered fin is configured to space the bottom lip away from a sump bottom. The chamfer is configured to compress the bellows in response to installation of the sump bottom along a direction parallel to a plane of the bottom lip.
Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
Some engine power is diverted to drive mechanical pump 20. Mechanical pump 20 draws fluid from sump 22, through filter 24, and delivers the fluid, at increased pressure, to valve body 26. The pressure at which fluid enters the valve body may be called line pressure. A network of control valves within the valve body deliver fluid to torque converter and gearbox components at desired pressures less than line pressure and at desired flow rates. Fluid drains from the control valves and from the gearbox back into sump 22.
The vertical distance 44 between the bottom of the sump and the entry point of fluid into the pump system is critical to system performance. If this distance is too small, it excessively constrains the flow of fluid. If the distance is too large, then air may be ingested into the pump system whenever fluid sloshes fore and aft or side to side due to vehicle acceleration or deceleration. To avoid air ingestion, the quantity of fluid in sump 22 is set such that the top surface 46 of the fluid is far enough above the entry point of fluid into the pump system. If the top surface 46 of the fluid is too high, rotating components will be partially submerged resulting in significantly higher parasitic drag and reduced fuel economy.
Controlling distance 44 is difficult in practice because a number of sources of variability add up. In addition to variability of the individual parts, the distance is impacted by variability in the joints between case halves, between the front case half and the pump, and between the pump and the filter. Variation of the vertical distance 44 between the bottom of the sump and the fluid entry point exacerbates the problems of ensuring adequate flow, avoiding air ingestion, and reducing parasitic drag. The nominal value of distance 44 must be set to ensure that the minimum distance at worst case tolerance stack-up provides sufficient flow. To avoid air ingestion, the fluid level must be set based on the maximum distance at another worst case tolerance stack-up.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.
