The present disclosure relates to hydraulic accumulators. More specifically, the present disclosure relates to start-stop hydraulic accumulators.
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Accumulators are relatively common components in hydraulic circuits and systems. As their name suggests, they are essentially storage devices that accumulate pressurized hydraulic fluid when a supply or flow of hydraulic fluid exceeds the consumption or demand of a system or device. Conversely, when the consumption or demand exceeds supply or flow, the previously stored fluid is exhausted from the accumulator to maintain the desired or necessary pressure or flow.
A typical vehicle powertrain includes an engine and a transmission. In certain powertrains, the engine is selectively turned on and off. That is, as the vehicle comes to a stop, the engine is automatically stopped under a predetermined stop condition, and then, under a predetermined restart condition, the engine is restarted. These powertrains may further include a hydraulic control system with an accumulator that is arranged to discharge a fluid to a torque transmitting device, such as, for example, a clutch when the engine is restarted, to accumulate the fluid when the engine is on, and to retain the fluid when the engine is turned off.
A hydraulic accumulator includes a housing with a pair of ends, a piston slidably disposed in the interior of the housing, and a biasing member that urges the piston towards one end of the housing. The accumulator further includes a fluid flow control device in communication with a fluid chamber defined by a face of the piston and the interior surface of the housing. The desired amount of fluid entering and exiting the fluid chamber is controlled by the fluid flow control device according to the desired pressure within the fluid chamber as determined by a pressure sensor which is also in communication with the fluid chamber.
Further features, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the views. In the drawings:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring now to the drawings, a hydraulic accumulator embodying the principles of the present invention is illustrated in
The accumulator 10 includes a housing 12 and an end cap 14 attached to one end of the housing 12. A seal 16 is disposed between the housing 12 and the end cap 14 to ensure that the housing 12 is leak free. The housing 12 is generally cylindrical in shape and includes an open end 18 and a closed end 20 opposite the open end 18. A supply line 22 is in communication with a fluid flow control device 24 which in turn is in communication with a pressure sensor 26. One end of the supply line 22 is connected to the fluid flow control device while the other end connects to a control system of an automatic transmission.
The piston 30 is located within the interior space 32 and is slidingly engaged with an inner surface 36 of the housing 12. A first outer face or surface 42 of the piston 30 and an inner surface 46 of the end cap 14 define an air filled chamber 48. A second outer face or surface 44 of the piston 30 and the inner surface 36 of the housing 12 define a fluid filled chamber 50. Accordingly, the piston 30 divides the interior space 32 of the housing 12 into the air chamber 48 and the fluid filled chamber 50. The fluid flow control device 24 and the pressure sensor 26 further communicate with the fluid filled chamber 50.
The piston 30 includes a circumferential channel or groove 60 which receives and retains a guiding ring 62. The guiding ring 62 is preferably fabricated of PTFE (Vespel) and assists in maintaining true axial orientation of the piston 34 within the housing 12. The piston 30 further includes a deeper circumferential channel or groove 64 which receives and retains a lip seal (ND ring) 66. The lip seal 66 may include a blade or wiper and functions as the primary seal between the piston 30 and the surface 36 of the housing 12. The piston 30 may also include a channel or groove 68 which receives and retains another guiding ring or bushing 70 to maintain axial orientation for an increased length (L) to diameter (D) ratio of the piston 30.
The supply line 22 and the fluid flow control device 24 define a fluid pathway into the fluid chamber 50. Specifically, fluid either enters or exits from the fluid chamber 50 through the flow control device 24. As fluid enters the fluid chamber 50, the pressure increases such that a force F is created. The force F created by the increased pressure of the fluid chamber 50 is greater than the biasing force BF. The force F exerted by the pressure of the fluid chamber 50 overcomes the biasing force BF, thereby urging the piston 30 to move in a direction towards the end cap 14. As fluid exits the fluid chamber 50, the fluid chamber 50 decreases in pressure such that the force F exerted by the fluid chamber 50 is now less than the biasing force BF, and the piston 30 is urged in a direction towards the end 52 of the housing 12 and returns to the seated position shown in
Various embodiments of the hydraulic accumulator 10 may have one or more of the following features and advantages. The piston 30 can be die cast with an integrated skirt. The biasing members 54 and 55 may be nested. The fluid flow control device 24 (which may be a solenoid) and the pressure sensor 26 are bolted to the housing 12. The charging and discharging of the accumulator 10 can occur through two separate paths. Oil flow through the flow control device 24 may occur through the same inlet and outlet. The housing 12 can be a one piece aluminum die cast and uses a precision machined piston bore. The housing 12 may be implemented as a one-piece bracket. The housing 12 may be impregnated with resin to provide zero leakage. The piston 30 may include an anodized hard coat.
The description of the invention is merely exemplary in nature and variations that do not depart from the gist 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.
This application claims the benefit of U.S. Provisional Application No. 61/538,286, filed Sep. 23, 2011, the entire contents of which are incorporated herein by reference.
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Number | Date | Country | |
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20130074967 A1 | Mar 2013 | US |
Number | Date | Country | |
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61538286 | Sep 2011 | US |