1. Field of the Invention
The present invention relates to an apparatus and a method for controlling a creep torque of a hybrid electric vehicle. More particularly, the present invention relates to an apparatus and a method for controlling a creep torque of a hybrid electric vehicle that outputs the creep torque to improve shift feel and fuel consumption of the hybrid electric vehicle.
2. Description of Related Art
A hybrid vehicle is a vehicle using two or more different kinds of power sources and is generally a vehicle that is driven by an engine that obtains a driving torque by burning fuel and a motor that obtains a driving torque with battery power.
Hybrid electric vehicles can be provided with optimum output torque, depending on how the engine and the motor are operated while the vehicles are driven by the two power sources, that is, the engine and the motor.
The hybrid vehicle may be formed in various structures using an engine and an electric motor as a power source, and a Transmission Mounted Electric Device (TMED) type hybrid vehicle in which a motor is attached to a transmission and in which an engine clutch is inserted between the transmission and the engine may implement an EV mode and an HEV mode using disconnection and connection of the engine clutch.
The hybrid electric vehicle generally uses a continuously variable transmission (CVT) or a stepped automatic transmission. Of these, the hybrid electric vehicle on which the stepped automatic transmission is mounted performs 3-1 shift or 2-1 shift before stopping for power performance and fuel consumption efficiency. In this shift process, a shift feel may be deteriorated when a torque variation is generated, a torque is less than 0, or a torque is too high.
Therefore, the hybrid electric vehicle controls a creep torque according to a predetermined creep torque map by using a motor control.
FIG. 4 and FIG. 5 are graphs illustrating a relation between a vehicle speed and a creep torque according to a conventional art.
As shown in FIG. 4, if the creep torque of the hybrid electric vehicle is increased and exceeds 0 torque before stopping and shifting, which results in deterioration of fuel consumption. Moreover, a shift feel may be deteriorated during shifting before stopping because a torque variation is generated.
Meanwhile, as shown in FIG. 5, the creep torque of the hybrid electric vehicle is sharply decreased by applying creep torque logic according to a predetermined creep torque map when the hybrid electric vehicle is running at a low speed with 1 shift stage. After that, the creep torque is increased again when the vehicle speed is decreased sufficiently, a driver may feel a sense of difference at this moment.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
USPTO Backgrounds
USPTO Backgrounds