Accumulator for Maintaining Hydraulic Pressure Following an Engine Restart

Abstract

A system for pressurizing transmission control elements includes an accumulator for containing pressurized fluid, first and second check valves, a booster valve supplied with accumulator pressure, and an actuator that causes the booster valve to open a fluidic connection between the accumulator and the control elements through the check valves in response to an engine restart signal

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates generally to a hydraulic system having a hydraulic accumulator for an automatic transmission, and more particularly to an accumulator that maintains hydraulic pressure for immediate engagement of the transmission following an engine restart.[0003]2. Description of the Prior Art[0004]In order to improve the fuel economy of vehicles that use an internal combustion engine for propulsion, some vehicles employ a stop-start strategy wherein, when the vehicle is stopped at a traffic light, for example, the engine is automatically turned off. Then when the driver releases the brake pedal to apply pressure to the accelerator pedal, the engine is automatically started to allow the vehicle to accelerate. For such vehicles that also have an automatic transmission, a need arises to maintain hydraulic pressure in the transmission so that the transmission can engage immediately after the engine is automatically ...

AI Technical Summary

Benefits of technology

[0008]The system maintains a full hydraulic charge pressure while the engine is off (under stop-start operating conditions), thus allowing the transmission to engage immediately when the engine is automatically restarted by electronically commanding the solenoid. The control assembly can operate to minimize oil leakage from the accumulator and eliminate need for frequent recharges due to use of a poppet valve and a sealed pressure balance valve.

[0009]The control system can release stored fluid with a minimum delay after electronically commanded due to use of spring compressed by the pressure balance valve.

[0011]The control system minimizes hydraulic losses between the hydraulic accumulator and the transmission hydraulic passage by using hydraulic valves with large passages and sealing elements.

Problems solved by technology

While this allows for the maintenance of hydraulic pressure while the engine is shut off, it may be more costly and require more packaging space than is desired.

Such a spring-loaded accumulator may require one hundred percent capacity fluid charge in order to mechanically latch the accumulator's piston, which may present an issue when frequent engine stop-start events occur.

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