Hill holding brake system for hybrid electric vehicles

Abstract

A hill holding function of a hybrid electric vehicle is initiated when the powertrain control module determines that a hill holding condition exists. In the hill holding condition, the electro-hydraulic brakes will provide brake torque to each wheel and the powertrain control module will turn off the internal combustion engine. The system can also detect a two footer condition where the vehicle operator requests both acceleration torque and brake torque simultaneously. The hill holding function of the hybrid electric vehicle in a two footer situation will apply the electro-hydraulic brakes and turn off the internal combustion engine. When the operator requests acceleration in either the hill holding or the two footer condition, the electric brake controller will transition the release of the electro-hydraulic brakes and the powertrain control module will turn on the internal combustion engine.

Description

BACKGROUND OF INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to a braking system for a hybrid electric vehicle and, more particularly, to a hill holding brake system for a hybrid electric vehicle. [0003] 2. Background Art [0004] A conventional wheeled automotive vehicle includes an internal combustion engine powered by fossil fuels. The desire to reduce emissions and consumption of fossil fuels in an internal combustion engine vehicle is well established. [0005] An electric vehicle comprises a battery and an electrical generator motor powerplant system to provide torque to a set of wheels. However, electric vehicles have limited range, limited power capabilities, and require a substantial amount of time to recharge the battery. Additionally, electric vehicles require the development of an extensive infrastructure to recharge the battery and service the electric vehicles. [0006] A hybrid electric vehicle includes a conventional internal comb...

AI Technical Summary

Benefits of technology

[0012] The present invention relates to a hill holding control method and system for a hybrid vehicle having an internal combustion engine, an integrated starter generator motor, and a electro-hydraulic brake system that provides hydraulic brake torque during a hill holding condition. The present invention improves the operating efficiency and driveability of the hybrid electric vehicle.

[0014] When a vehicle operator requests acceleration during the hill holding condition, the electronic brake control system reduces electro-hydraulic brake torque at the wheels and the powertrain control module turns on the internal combustion engine. A vehicle transmission is engaged for seamless acceleration following the hill holding brake application.

[0017] 1) improves the operating efficiency of the hybrid electric vehicle by not using the integrated starter generator motor to provide this function and eliminates the need for additional cooling for the integrated starter generator motor;

[0018] 2) improves the drive-ability of the hybrid electric vehicle;

[0021] 5) allows automatic transmissions a more efficient method of hill holding since the clutch pressure does not have to be maintained to provide hill holding; and

[0022] 6) allows hill holding to be performed more efficiently than present day transmission hill holding systems by not using the transmission to provide this function saving energy by not keeping the clutch pressure on and eliminating the need for additional cooling for the transmission.

Problems solved by technology

However, electric vehicles have limited range, limited power capabilities, and require a substantial amount of time to recharge the battery.

The internal combustion engine in a hybrid electric vehicles wastes fuel and produces undesirable emissions to hold the vehicle on a hill because the internal combustion engine must continue to operate while the vehicle is stopped.

However, the use of the integrated starter generator motor in a hybrid electric vehicle wastes battery power and requires additional cooling during hill holding conditions.

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