Variable Brake Pressure Release for Creep Groan Reduction

The patent applies dynamics by making the brake pressure release rate variable rather than constant. The release rate is adjusted based on engine drive force stability: initially set high to quickly exit the stick-slip occurable range and reduce creep groan, then reduced to a lower level after engine drive force stabilizes to prevent engine stall. This dynamic adjustment resolves the contradiction between reducing creep groan and ensuring engine restart stability.

The patent changes the parameter of brake pressure release rate from a fixed value to a variable value that changes based on engine drive force stability. By monitoring whether the engine drive force has stabilized and adjusting the release rate accordingly (high initially, then lower after stabilization), the system resolves the contradiction between minimizing creep groan duration and preventing engine stall.

The patent makes the release rate dynamic by initially setting it at a higher level (first gradient equivalent) to quickly reduce brake pressure through the stick-slip occurable range, thereby reducing creep groan. After engine drive force stabilizes, the release rate is reduced to a lower level (second gradient equivalent) to prevent vehicle jump start and ensure smooth starting performance. This dynamic adjustment resolves the contradiction between reducing creep groan and maintaining starting performance.

The patent applies preliminary action by first rapidly reducing brake pressure through the dangerous stick-slip occurable range before the engine drive force fully stabilizes, thereby preventing creep groan from occurring in the first place. This preliminary high-rate release prevents the harmful frictional engagement repetition, and subsequent lower-rate release ensures smooth vehicle start without jump start.