Patent Application
20140026988
The invention relates to a control system for an automatic transmission, and more particularly to a control system for actively maintaining hydraulic fluid level in the sump tank of an automatic transmission.
A typical automatic transmission includes a hydraulic control system that is employed to provide cooling and lubrication to components within the transmission and to actuate a plurality of torque transmitting devices. The hydraulic control system typically includes a sump that collects hydraulic fluid from the remainder of the hydraulic control system, gathers it to a pool of hydraulic fluid to be suctioned back into the hydraulic control system. A minimum level of hydraulic fluid is required in the sump in order to feed the hydraulic control system for all ranges of transmission operation and dynamic movement of the hydraulic fluid in the sump. Due to the minimum amount of hydraulic fluid requirements, the level of the hydraulic fluid in the sump interferes with the rotating components of the transmission. The rotating components, including gears, clutch plates, and interconnecting members; traveling through the pool of hydraulic fluid experience a great increase in drag and in turn decreases the efficiency of the transmission.
While previous hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within transmissions which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness, is essentially constant. Accordingly, there is a need for an improved, cost-effective hydraulic control system for use in a hydraulically actuated automatic transmission.
A transmission having a hydraulic fluid control system is provided. The control system includes a sump tank, a front cover, a separation wall, and a flow control valve. The sump tank is attached to a bottom end of the transmission and includes a pick-up tube and filter. The front cover is attached to the transmission and includes an overflow tube and a hydraulic fluid input. The overflow tube has a first end in fluid communication with the sump tank and a second end in fluid communication with the front cover. The wall hydraulically separates the sump tank and the front cover and wherein the first end of the overflow tube is disposed in the wall. The flow control valve is disposed in the wall between the sump tank and front cover. The flow control valve is in communication with each of the sump tank and the front cover. The flow control valve is open when the transmission is going through an extreme maneuver and requires a greater amount of hydraulic fluid in the sump tank and the flow control valve is closed during normal transmission operation.
In one example of the present invention, the second end of the overflow tube is at a distance H above a bottom of the front cover.
In another example of the present invention, the hydraulic fluid input of the front cover collects hydraulic fluid from the transmission and directs the hydraulic fluid into the front cover.
In yet another example of the present invention, the overflow tube has a 90° bend between the first end and the second end.
In yet another example of the present invention, the control valve is disposed in the wall at a distance L from a bottom of the front cover.
In yet another example of the present invention, the extreme maneuver includes one of a hard deceleration, a hard acceleration, a sharp turn, a steep ascent, and a steep descent.
Further features and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
With reference to
The portion of the hydraulic control system 10 is operable to collect hydraulic fluid 24 from various sources in the transmission and provide a source of hydraulic fluid 24 for the rest of the hydraulic control system. More particularly, the front cover 14 is filled with hydraulic fluid 24 by a fluid input passage 20 which collects hydraulic fluid 24 from hydraulic control system leakage such as from spool valves, pressure control solenoids, excess control valve exhaust, etc. The sump 12 is a tank or reservoir preferably disposed at the bottom of a transmission housing and proximate the front cover 14. The wall 15 hydraulically separates the front cover 14 and the sump 12. The control valve 16 is placed in the wall at a distance L from the bottom of the front cover allowing the front cover 14 to selectively communicate with the sump 12. The control valve 16 is solenoid operated and selectively controlled to allow hydraulic fluid 24 to flow from the front cover 14 to the sump 12 under certain operating conditions. The overflow tube 18 has a first and a second end 18A, 18B with a 90° bend 18C in between the two ends 18A, 18B. The first end 18A of the overflow tube 18 is placed in the wall 15 so that the interior of the overflow tube 18 communicates with the sump 12. The second end 18B of the overflow tube 18 extends to a height H above the bottom of the front cover 14. The overflow tube 18 also allows hydraulic fluid 24 to flow from the front cover 14 to the sump 12, however, only when the level of hydraulic fluid 24 in the front cover 14 reaches a certain height H determined by the height H of the overflow tube 18. When the hydraulic fluid 24 in the front cover 14 reaches the height H, the hydraulic fluid 24 flows into the second end 18B of the overflow tube 18 and into the sump 12. The hydraulic fluid 24 is forced from the sump 12 and communicated throughout the remainder of the hydraulic control system via a pump 26 and the fluid pick-up tube and filter 22. The pump 26 is preferably driven by an engine (not shown) and may be, for example, a gear pump, a vane pump, a gerotor pump, or any other positive displacement pump.
The hydraulic control system 10 as shown in
Referring now to
The description of the invention is merely exemplary in nature and variations that do not depart from the general essence of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
