Engine stop control method of power split-parallel HEV system

Abstract

An engine stop control method of a power split-parallel hybrid electric vehicle (HEV) system may include: determining any one driving mode among an EV mode, a power split mode and a parallel mode, corresponding to a driver's request; recognizing and deciding whether the driving mode is a mode required to stop an engine; stopping the engine; and performing kill torque (TQ) control on the revolution speed of the engine through a motor so that the revolution speed of the engine reaches 0 rpm. Accordingly, the revolution speed of the engine can be reduced down to an rpm lower than that of the conventional art, thereby promoting fast mode conversion.

Claims

1. An engine stop control method of a power split-parallel hybrid electric vehicle (HEV) system, the method comprising steps of: determining any one driving mode among an EV mode, a power split mode and a parallel mode, corresponding to a driver's request; recognizing and determining whether the driving mode is a mode required to stop an engine; and upon determination that the driving mode is a mode required to stop an engine, stopping the engine and performing kill torque (TQ) control on a revolution speed of the engine through a motor until the revolution speed of the engine reaches 0 rpm, wherein the performing of the kill TQ control includes: performing the kill TQ control through the motor; determining whether the revolution speed of the engine reaches a specific rpm; after removing the kill TQ when the revolution speed of the engine reaches the specific rpm, outputting the TQ of the motor as a value obtained by offsetting friction TQ of the engine; and performing feedback control on the TQ of the motor, which offsets the friction TQ, until the revolution speed of the engine is converged to 0 rpm.

2. The method of claim 1, wherein the step of determining the driving mode includes: allowing the driver to monitor power required in the system; and selecting a driving mode according to the driver and the power required in the system.

3. The method of claim 2, further comprising a step of: upon determination that the driving mode is a mode not required to stop the engine, repeating the step of allowing the driver to monitor the power required in the system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

(2) FIG. 1 is a graph in which kill torque (TQ) control is performed by using HSG when a conventional hybrid electric vehicle (HEV) is stopped;

(3) FIG. 2 is a flowchart illustrating an engine stop control method of a power split-parallel HEV system according to an embodiment of the present invention; and

(4) FIG. 3 shows kill TQ and rpm control graphs through the engine stop control method of the power split-parallel HEV system according to the embodiment of the present invention.

(5) It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

(6) In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

(7) Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

(8) An engine stop control method of a power split-parallel hybrid electric vehicle (HEV) system according to an embodiment of the present invention, as shown in FIG. 2, is different from the conventional art in control for reducing impact applied to a one-way clutch (OWC). The engine stop control method is performed as follows with reference to FIGS. 2 and 3. FIG. 2 is a flowchart illustrating an engine stop control method of a power split-parallel HEV system according to an embodiment of the present invention. FIG. 3 shows kill TQ and rpm control graphs through the engine stop control method of the power split-parallel HEV system according to the embodiment of the present invention.

(9) First, a driving mode among an EV mode, a power split mode and a parallel mode is determined corresponding to a driver's request (S100).

(10) It is recognized and decided whether the driving mode is a mode required to stop an engine (S200).

(11) After that, the engine is stopped. That is, the engine has been stopped when engine fuel is cut, but a crank is continuously rotated by a driving speed (S300).

(12) Next, kill TQ control is performed on the revolution speed of the engine through a motor MG1 until the revolution speed of the engine reaches 0 rpm (S400).

(13) A specific rpm is experimentally determined as a generator (MG2) performs reaction force control on the MG1 (MG2 TQ=reaction force TQ+demand TQ) while the kill TQ control is performed through the MG1. The specific rpm may be set to an rpm lower than the engine rpm of the conventional HEV.

(14) In this state, in the performing of the kill TQ control (S400), the kill TQ control is performed through the MG1 (S410), thereby deciding whether the engine reaches the specific rpm, for example, a predetermined rpm A, or less (S420).

(15) Thus, after the kill TQ is removed when the engine reaches the specific rpm, the TQ of the MG1 is output as a value that offsets friction TQ of the engine (S430).

(16) The output TQ of the MG1 is a value obtained by considering a gear ratio, and increases with a constant slope from the kill TQ to the TQ obtained by offsetting the friction TQ.

(17) Then, feedback control is performed on the TQ of the MG1, which offsets the friction TQ, until the revolution speed of the engine is converged to 0 rpm (S430 and S440).

(18) Meanwhile, the determining of the driving mode (S100) includes allowing the driver to monitor power required in the system (S110); and selecting a driving mode according to the driver and the power required in the system (S120).

(19) In a case where the driving mode is a mode not required to stop the engine in step S200, feedback to the allowing of the driver to monitor the power required in the system (S110) is performed.

(20) According to the method described above, as shown in FIG. 3, control when the engine is stopped in a state in which a vehicle is stopped according to time can be identify through graphs.

(21) In the graphs, P1 designates a section in which the kill TQ is controlled to reduce the revolution speed of the engine, P2 designates a section in which the TQ is changed with a constant slope up to the TQ obtained by offsetting the friction TQ after the kill TQ is removed, and P3 designates a section in which the reverse revolution of the engine is prevented by offsetting the friction TQ of the engine (feedback control is performed so that the revolution speed of the engine is converged to 0 rpm).

(22) According to the present invention configured as described above, the revolution speed of the engine can be reduced down to an rpm lower than that of the conventional art, thereby promoting fast mode conversion. In addition, the inertia of the engine can be offset at the time when the engine is stopped, so that it is possible to perform kill TQ control down to the rpm lower than that of the conventional art.

(23) Further, the inertia of the engine can be reduced by generating the TQ that offsets the friction TQ. Thus, it is possible to reduce impact applied to an OWC, thereby improving the durability of the system. In addition, the control of reducing the inertia of the engine can not only reduce impact applied to the OWC but also allow a driver not to feel the impact, thereby improving the driver's satisfaction.

(24) The aforementioned method may be implemented by a controller including computer storage medium encoding computer executable instructions that when executed by one or more processors of the controller, cause the one or more processors to perform the steps of the aforementioned method. The controller may be integrated to an electronic control unit (ECU) or of the vehicle. The controller may include various signal lines for providing engine status such as the rmp of the engine, to the controller, and various control lines for transmitting control signals, such as kill TQ control signal and MG1 TQ signal, to the respective components of the vehicle, from the controller.

(25) The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.