Method for learning the kisspoint of an engine clutch in a hybrid vehicle

Abstract

The present disclosure provides a method for learning a kisspoint of an engine clutch in a hybrid vehicle, which performs kisspoint learning of an engine clutch while driving by learning hydraulic pressure at the time when motor torque varies by gradually increasing clutch hydraulic pressure in an open state of the engine clutch when a driving load of a vehicle is constant to increase a kisspoint learning frequency of the engine clutch and improve kisspoint accuracy.

Claims

1. A method for learning a kisspoint of an engine clutch in a hybrid vehicle, the method comprising: determining whether a kisspoint learning entrance condition is satisfied in order to determine whether kisspoint learning of the engine clutch is possible while driving a vehicle; and performing kisspoint detection for the kisspoint learning of the engine clutch while driving when it is determined that the kisspoint learning entrance condition is satisfied, wherein when determining whether the kisspoint learning entrance condition is satisfied, it is determined that the kisspoint learning entrance condition is satisfied when a kisspoint learning history of the engine clutch does not exist within a driving cycle of ignition-off after ignition-on of the vehicle, a driving load of the vehicle while driving is constantly maintained, and a battery SOC exists within a predetermined range.

2. The method of claim 1, wherein when it is determined that the kisspoint learning entrance condition is satisfied, a state of the engine clutch is determined before performing the kisspoint detection, and when the engine clutch is in a lock-up state, the lock-up state of the engine clutch is transited to an open state.

3. The method of claim 1, wherein during performing the kisspoint detection, a motor is controlled at a constant speed to output a driver's request torque, the engine is controlled to a speed value acquired by combining a motor rotational speed and a motor torque variation threshold value, and a hydraulic pressure of the engine clutch is gradually increased stepwise to learn hydraulic pressure when torque of the motor, which maintains the constant speed, varies at a kisspoint of the engine clutch.

4. The method of claim 3, wherein the motor rotational speed is the speed value of the motor controlled to a speed for outputting the driver's request torque and the motor torque variation threshold value is the speed value capable of causing torque variation of the motor at the time when both ends of the engine clutch contact each other.

5. The method of claim 1, wherein the predetermined range for determining the battery SOC as a reference range for determining whether the battery SOC satisfies the kisspoint learning entrance condition of the engine clutch is determined to ensure that a vehicular drive force only by the motor is sufficient in entering the kisspoint learning of the engine clutch.

6. The method of claim 1, wherein, when it is determined that all of the kisspoint learning entrance conditions are satisfied, a gear step of a transmission is maintained while driving and the kisspoint learning of the engine clutch is entered.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other features of the present disclosure 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 disclosure, and wherein:

(2) FIG. 1 is a flowchart for describing a method for learning a kisspoint of an engine clutch in a hybrid vehicle according to the present disclosure;

(3) FIG. 2 is a diagram for describing a kisspoint detection condition in learning the kisspoint of the engine clutch according to the present disclosure;

(4) FIG. 3 is a diagram illustrating hydraulic pressure of the engine clutch, and rotational speeds and output torque of an engine and a motor depending on a kisspoint learning process of the engine clutch according to the present disclosure; and

(5) FIG. 4 is a diagram illustrating that hydraulic pressure at the time when the motor torque varies is learned with a new kisspoint at the time of learning the kisspoint of the engine clutch in the related art.

(6) 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 disclosure. The specific design features of the present disclosure 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.

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

DETAILED DESCRIPTION

(8) Hereinafter, reference will now be made in detail to various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings and described below. While the disclosure will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the disclosure to those exemplary embodiments. On the contrary, the disclosure 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 disclosure as defined by the appended claims.

(9) Hereinafter, reference will now be made in detail to various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings and described below.

(10) In the present disclosure, kisspoint learning of an engine clutch may be performed while a vehicle stops and the kisspoint learning of the engine clutch may be performed while driving.

(11) However, since technology that performs the kisspoint learning of the engine clutch while the vehicle stops, that is, a transmission is positioned at a parking step (P step) or a neutral step (N step) is known technology, a detailed description thereof will be omitted.

(12) FIG. 1 is a flowchart for describing a method for learning a kisspoint of an engine clutch in a hybrid vehicle according to the present disclosure.

(13) Referring to FIG. 1, it is determined whether a kisspoint learning entrance condition is learned in order to determine whether kisspoint learning of the engine clutch is possible while driving a vehicle.

(14) The learning entrance condition includes a kisspoint learning history, a driving load of the vehicle while driving and a battery status of charge (SOC) while driving.

(15) In order to determining the kisspoint learning entrance condition of the engine clutch while driving, it is determined whether the kisspoint learning point of the engine clutch exists within one driving cycle (until ignition-off from ignition-on of the vehicle). It is further determined whether the driving load is constant while driving when the kisspoint learning history does not exist according to a result of the determination.

(16) When it is determined that the driving load of the vehicle is constant, it is determined whether the battery SOC is within a predetermined range by detecting the battery SOC while driving. This is done to check whether the battery SOC is sufficient, as a vehicular drive force must be provided only by a motor while entering kisspoint learning.

(17) In addition, when it is determined that the driving load of the vehicle is not constant, the kisspoint learning entrance is not performed.

(18) When a driving mode in which the driving load of the vehicle is constant, for example a driving mode in which the vehicle is driven at a constant speed in an auto cruise mode, the kisspoint learning entrance may be performed.

(19) According to a result of determining whether the learning entrance condition is satisfied, it is determined whether the learning entrance condition is satisfied when the engine clutch kisspoint learning history does not exist within one same driving cycle, whether the driving load of the vehicle while driving is constantly maintained and whether the battery SOC exists within the predetermined range.

(20) The predetermined range for determining the battery SOC condition as a reference range for determining whether the battery SOC value satisfies the kisspoint learning entrance condition of the engine clutch is determined to ensure the vehicular drive force only by the motor is sufficient in the kisspoint learning entrance of the engine clutch.

(21) When it is determined that all of the kisspoint learning entrance conditions are satisfied, a current step (gear step) of a transmission is maintained while driving and the kisspoint learning of the engine clutch is entered.

(22) By determining the state of the engine clutch, a kisspoint detection process for the kisspoint learning is performed immediately when the engine clutch is in an open state. When the engine clutch is in a lock-up (or closed) state, the lock-up state of the engine clutch is transited to the open state of the engine clutch and thereafter, the kisspoint detection process for the kisspoint learning is performed. The kisspoint detection process for the kisspoint learning of the engine clutch in the open state of the engine clutch is then performed.

(23) When the kisspoint of the engine clutch is detected, the motor is controlled at a constant speed to output driver's requested torque (torque requested by a driver for driving the vehicle) to maintain a transmission output speed, and the engine is controlled at a speed value acquired by adding a motor rotational speed (motor rpm) and a motor torque variation threshold value (Δrpm).

(24) The motor rotational speed (motor rpm) is a speed value of the motor controlled at a speed for outputting the driver's output torque. The motor torque variation threshold value, a speed value for enabling the kisspoint of the engine clutch to be detected, is set to a value outside a range that may influence drivability while varying the motor torque at the time of detecting the kisspoint of the engine clutch.

(25) The motor torque variation threshold value (Δrpm) is determined through testing to cause the motor torque to vary at the time when both ends of the engine clutch contact each other under an actual condition.

(26) The hydraulic pressure of the engine clutch is then gradually increased (see FIG. 2). The hydraulic pressure of the engine clutch is increased stepwise at predetermined intervals while speed-controlling the motor and the engine to detect hydraulic pressure at the time when the output torque of the motor, which maintains the constant speed, varies and the system learns the hydraulic pressure at that time with a new kisspoint of the engine clutch.

(27) After learning the new kisspoint is completed within one driving cycle, the vehicle returns to a general driving pattern.

(28) After the vehicle returns to the general driving pattern, the engine is output-controlled by an engine operation point while driving, the motor is output-controlled by a motor operation point while driving, the step (gear step) of the transmission is controlled according to a vehicle speed while driving, and the engine clutch is controlled in the open or lock-up state according to the driving mode (HEV mode, EV mode).

(29) FIG. 3 illustrates the hydraulic pressure of the engine clutch. The rotational speeds and output torque of the engine and the motor depending on a kisspoint learning process of the engine clutch while the hybrid vehicle is being driven illustrates an interval of preparing for the kisspoint learning in the open state of the engine clutch when the kisspoint learning entrance condition is satisfied, an interval of performing the kisspoint detection process for the kisspoint learning of the engine clutch while driving, and an interval of returning to the general diving pattern after completing the kisspoint learning.

(30) The kisspoint learning of the engine clutch may be performed by in-vehicle control units, for example, by a hybrid control unit (HCU), an engine control unit (ECU), a motor control unit (MCU) or a transmission control unit (TCU).

(31) The disclosure has been described in detail with reference to preferred 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 disclosure, the scope of which is defined in the appended claims and their equivalents.