KR20090040930A - Engine restart control method of hybrid electric vehicle in electric oil pump fail - Google Patents

Abstract

A method for controlling an engine to restart when a motor oil pump of a hybrid vehicle has a trouble is provided to prevent impact of a transmission effectively controlling the number of rotation of the engine through ISG speed control. A method for controlling an engine to restart when a motor oil pump of a hybrid vehicle comprises the following steps of: driving an electronic oil pump in an idle stop state; stopping drive of the electronic oil pump after determining troubles; beginning engine motoring by ISG; increasing the number of revolution of an engine; maintaining the number of revolution by controlling the drive of the ISG; and completing ISG motoring termination and engine restart.

Description

Engine restart control method of hybrid electric vehicle in electric oil pump fail}

The present invention relates to a method for controlling an engine restart when an electric oil pump fails in a hybrid vehicle, and more particularly, a control capable of restarting the engine without a vehicle shock when the electric oil pump for an automatic transmission or a continuously variable transmission fails in a hybrid vehicle. It is about a method.

In general, a hybrid vehicle in a broad sense means to drive a vehicle by efficiently combining two or more different power sources, but in most cases, a driving force is driven by an electric motor driven by an engine and a battery power that use a fuel to obtain driving power. Means a vehicle to obtain, it is called a hybrid electric vehicle (HEV).

In response to the recent demand for improving fuel economy and developing more environmentally friendly products, research on hybrid vehicles is being actively conducted.

In the hybrid vehicle, the EV mode is a pure electric vehicle mode that selectively runs only by the rotational power of the motor, the engine mode that runs only by the rotational force of the engine, and the rotational force of the engine as the main power. And HEV (Hybrid Electric Vehicle) mode, which is an auxiliary mode that uses the rotational power of a motor driven by battery power as an auxiliary power, and recovers braking and inertial energy from the motor through electric power generation and charges the battery when the vehicle is driven by braking or inertia. Is driven in Regenerative Braking (RB) mode.

As described above, the hybrid vehicle employs a structure in which two power sources, that is, an engine and a motor, are properly combined to induce fuel efficiency improvement by power assistance of a motor driven by battery power when the vehicle starts or accelerates.

On the other hand, in the existing vehicle equipped with an automatic transmission or a continuously variable transmission using hydraulic pressure, the oil pump, which is the source of hydraulic pressure, is directly connected to the crank shaft of the engine, so that hydraulic pressure can be generated only while the engine is rotating.

However, in the case of hybrid vehicles, the engine stops when idling for a certain period of time to improve fuel economy, and when the brake pedal is released or the pedal is released, the engine automatically restarts the idle stop & go function. Equipped.

To apply the idle stop function that completely cuts fuel to stop unnecessary fuel consumption when the vehicle is stopped, such as waiting for a signal, in an existing hybrid vehicle, the oil pump (mechanical oil pump) in the automatic transmission during the idle stop is applied. (I) does not rotate, so no line pressure is generated in the transmission, so that the friction elements (clutch and brakes) for maintaining the forward 1 speed (D range 1 speed) in the planetary gearbox cannot be caught. In case of CVT, the gear ratio cannot be maintained because there is no line pressure.

In addition, when the driver releases the brake pedal or restarts the accelerator pedal for restarting, the engine restarts. In this case, as the engine speed increases, the speed of the automatic transmission oil pump also increases.

At this time, the line pressure in the automatic transmission is sharply increased, so that a friction element for maintaining the forward 1 speed is rapidly applied, which is immediately represented as a vehicle shock, causing the driver's discomfort and damage to the friction element.

In order to prevent such a shock, there may be a way to perform neutral control at the start, but this requires a forward speed gear to be applied after starting in the neutral state and the line pressure is stabilized, thus making the vehicle start a lot of time. Difficult to apply to real vehicles.

As described above, there is a technology for installing an additional auxiliary hydraulic system for maintaining the line pressure in the transmission during the idle stop to solve the problem appearing when applying the idle stop function to the existing automatic transmission vehicle.

That is, an external electric oil pump that can be controlled separately from the engine driving to supply the necessary hydraulic fluid while the engine is stopped and to generate the line pressure is provided, and an existing mechanical oil pump is provided in the automatic transmission, and the external of the automatic transmission is provided. An external electric oil pump is installed.

In such a hybrid vehicle, an external electric oil pump is interlocked with a mechanical pump provided in an automatic transmission to supply hydraulic oil.In order to generate pressure in the same hydraulic line, the existing mechanical oil pump and an electric transmission in the automatic transmission are operated. The oil pump is configured in parallel to the hydraulic line of the transmission.

1 is a diagram illustrating a configuration in which an auxiliary hydraulic system including an electric oil pump is added to an existing automatic transmission hydraulic system in a hybrid vehicle, and a conventional mechanical oil pump 10 is a transmission line pressure while an engine is started. It plays a role of generating, and during the idle stop section, the electric oil pump 20 plays a role of generating the transmission line pressure.

In addition, a check valve is provided between the mechanical oil pump 10 and the electric oil pump 20 to prevent oil from flowing back to the hydraulic line side of the electric oil pump 20 installed in parallel while the mechanical oil pump 10 is operating. 21 is installed.

2 is a view for explaining a control state of the electric oil pump in the normal state, it will be described with reference to this control of the conventional electric oil pump as follows.

First, when the vehicle is stopped, the vehicle enters the idle stop function, the fuel injection is stopped, the engine speed is lowered, and the pressure in the transmission hydraulic line is reduced.

At this time, the driving of the electric oil pump is started. Since the transmission line pressure is not large during the idle stop period, the driving duty of the electric oil pump motor is controlled to be low at a set low duty to maintain only a small line pressure. Reduces the time it takes for the line pressure to rise on restart, improving the vehicle's starting response.

In addition, when the engine of the vehicle is restarted, the driving duty of the electric oil pump motor is controlled to high duty to increase the pressure of the hydraulic line in the transmission rapidly, thereby applying the friction element of the planetary gear in advance and rotating the engine. To allow transmission of the transmission input torque.

This makes it possible to avoid the occurrence of a vehicle shock even after the engine is restarted thereafter.

Subsequently, when the engine oil is started, the mechanical oil pump stops driving the electric oil pump when it reaches an idling speed that can generate sufficient pressure.

When the auxiliary hydraulic system including the electric oil pump is applied as described above, shock may occur when the engine is restarted after the idle stop in a hybrid vehicle equipped with an automatic transmission (A / T) or continuously variable transmission (CVT) using hydraulic pressure. It becomes possible.

Another way to avoid shocks during restart is to use a neutral control method that puts the transmission in neutral at start-up and prevents engine torque from being transferred to the wheels.

In this case, it is difficult to apply it to the actual vehicle because the response to the vehicle oscillation is reduced because the control conversion is required to the forward 1 speed after starting the engine, and the driver can feel the discomfort caused by the shift even when switching from neutral to drive. to be.

However, when the electric oil pump fails in a hybrid vehicle to which an auxiliary hydraulic system (electric oil pump) is applied, it is not possible to reduce the impact during restart through conventional control.

FIG. 3 is a view illustrating a shock phenomenon occurring when a conventional auxiliary hydraulic system breaks down, and using an existing integrated starter and generator (ISG) when a secondary hydraulic system (electric oil pump) fails. When the engine is started quickly, the mechanical oil pump in the automatic transmission rotates along with the engine rotation, thereby rapidly increasing the A / T line pressure.

In this case, friction elements such as clutches and brakes in the automatic transmission are suddenly engaged, and the amount of torque transmission from the engine to the wheels is suddenly changed, resulting in an impact on the vehicle.

In addition, if the hybrid oil motor is prohibited from starting when the electric oil pump fails, the driver will not be able to start unexpectedly. Therefore, the existing control logic is difficult to apply.

Therefore, in the related art, only a method of prohibiting the idle stop itself and restarting has been proposed if it is determined that the electric oil pump has a failure and is determined to be in a failure state.

Therefore, the present invention has been invented to solve the above problems, a hybrid vehicle that can restart the engine without the impact in the vehicle in the event of a failure of the automatic oil pump or the electric oil pump for continuously variable transmission in the idle stop state of the hybrid vehicle. Its purpose is to provide a method for controlling engine restart of the engine.

In order to achieve the above object, the present invention, in the engine restart control method for restarting the engine in the event of failure of the electric oil pump in the idle stop state of the hybrid vehicle, (a) driving the electric oil pump in the idle stop state But not determining whether the electric oil pump has failed and stopping the driving if the electric oil pump has failed; (b) driving the ISG and starting engine motoring by the ISG when it is determined that the engine restart condition is based on the vehicle information; (c) The rotation of the ISG until the pressure of the hydraulic line in the transmission rises by the operation of the mechanical oil pump in the transmission until the pressure sensing value of the hydraulic sensor installed in the hydraulic line reaches the target line pressure set as the friction element tightening pressure. Controlling the speed to gently increase the engine speed; (d) controlling the driving of the ISG when the sensing value of the hydraulic sensor reaches a target line pressure, thereby maintaining the engine speed constant for a predetermined time; (e) After the set time, increase the rotation speed of the ISG while the friction elements in the transmission are fully engaged, and increase the engine speed to the idle speed.When the engine speed reaches the idle speed, start the fuel injection to start the ISG motor. And completing the ring termination and engine restart.

Here, in the step (a), characterized in that the electric oil pump failure is determined on the basis of the signal of the hydraulic sensor installed in the hydraulic line in the transmission while the electric oil pump is driven during the idle stop.

In addition, if the pressure sensing value of the hydraulic sensor is less than the normal line pressure estimate, it characterized in that it is determined that the electric oil pump failure.

According to the engine restart control method of the present invention having the above characteristics, it is possible to effectively control the engine speed through the ISG speed control in accordance with the pressure state of the hydraulic line in the transmission can effectively prevent the shock in the transmission at restart, restart The driver's discomfort and anxiety due to heavy shocks can be eliminated. In particular, the engine can be restarted in the event of a failure of the electric oil pump.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, the engine start speed (ISG) is controlled by controlling the speed of the ISG based on the line pressure (pressure in the hydraulic line) in the transmission sensed by the hydraulic sensor when the engine is restarted in the failure state of the auxiliary hydraulic system (external electric oil pump). By controlling the number of revolutions of the engine motorized by) to minimize the occurrence of the impact of the vehicle.

For reference, the integrated starter and generator (ISG) is referred to as an integrated start generator, which integrates the starting and generating functions.

Normally, when the engine restart is requested, the ISG starts driving to start engine motoring, and when the engine rotates to reach a predetermined idle speed, the fuel injection starts and the motoring ends and starts the engine. Done is done.

4 is a flowchart illustrating an idle stop mode entry process, and FIG. 5 is a flowchart illustrating an engine restart process according to the present invention.

6 is a diagram showing an engine motoring control state and a line pressure control state according to the engine restarting method of the present invention, and FIG. 7 is a flowchart of an engine restarting mode in the case of a pump failure according to the present invention.

First, referring to FIG. 4, in a hybrid vehicle, a vehicle controller (VCU) obtains various vehicle information such as a vehicle speed, a brake pedal switch signal, a coolant temperature, and the like through a CAN communication while driving (S10) to satisfy an idle stop entry condition of a vehicle. It determines whether it is (S21-S23).

Here, when it is determined from the vehicle information that the idle stop entry condition is satisfied (S30), the motor controller P-MCU for controlling the motor of the electric oil pump (EOP) is connected to the power line of the electric oil pump motor. Short circuit or open circuit failure is determined (S40).

At this time, when it is determined that the short-circuit or disconnection failure of the power line of the electric oil pump motor (S50), the vehicle controller recognizes the short-circuit or disconnection of the pump according to the signal of the motor controller in the driving mode without entering the idle stop mode. Still other mode transition conditions are determined.

Typical idle stop entry conditions include a condition where the brake pedal switch is on, the vehicle speed = 0 km / h, and the like as shown in the example of FIG. 4.

On the other hand, when the electric oil pump is in a normal state, that is, when it is not a short circuit or disconnection failure, the vehicle controller recognizes that it is not a short circuit or disconnection failure from the signal of the motor controller and performs normal control for entering the idle stop mode. In addition, when entering the idle stop, the engine controller ECU performs fuel cut control for stopping the engine according to the signal of the vehicle controller (S60).

After the vehicle enters the idle stop mode, the motor controller P-MCU of the electric oil pump drives the motor of the electric oil pump at a predetermined low duty during the idle stop (as shown in FIG. 3). As shown).

At this time, the vehicle controller determines the mechanical failure of the electric oil pump on the basis of the pressure of the transmission hydraulic line which is the sensing value of the hydraulic sensor during the operation of the electric oil pump, and if it is determined that the failure state, the electric oil pump through the motor controller To stop the motor drive (pump drive stop).

Normally, the failure of auxiliary hydraulic system can be categorized into electrical failure such as short circuit or open of motor, power line, and mechanical failure of hydraulic system caused by breakage of oil pump and attached hydraulic line. When the motor controller determines that the power supply line is shorted or disconnected in the engine starting state, entry to the idle stop mode is prohibited as described above.

However, the above mechanical failure can be discriminated based on the current sensing by the current sensor and the pressure sensing value by the hydraulic sensor of the transmission hydraulic line only during the operation of the electric oil pump. Mechanical failures such as breakage of the oil pump and the hydraulic lines attached to the pump are determined by measuring the transmission line pressure during low duty operation of the electric oil pump at idle stop and then comparing the measured line pressure with the normal line pressure estimate. can do.

If the pressure sensing value of the hydraulic sensor installed in the transmission hydraulic line is less than the normal line pressure estimate, it may be determined that the pump is a mechanical failure because the normal hydraulic pressure is not provided by the pump.

Since the operation of the electric oil pump is stopped in the engine start state other than the idle stop mode, only a short circuit or disconnection of the power line can be judged, and it is difficult to determine all the failure states of the auxiliary hydraulic system. A fault condition (mechanical failure) is allowed but the idle stop mode can be entered.

Accordingly, in the present invention, if the vehicle enters the idle stop mode, the vehicle controller (or the motor controller of the electric oil pump) during the operation of the electric oil pump determines the mechanical failure of the electric oil pump based on the transmission line pressure. If it is determined that the failure of the electric oil pump (EOP Fail) will stop the operation of the pump motor through the motor controller (P-MCU).

FIG. 5 illustrates a process of restarting the engine in an idle stop state. When the vehicle controller VCU determines a normal idle stop release and restart condition from vehicle information such as a brake pedal switch signal, coolant temperature, and SOC ( S71 ~ S74), motor restart (P-MCU) of electric oil pump, motor controller (I-MCU) to control ISG, engine restart (constant control) with cooperative control with engine controller (ECU) to control fuel injection Normal engine restart or engine restart in case of a pump failure).

Here, if the normal condition of the electric oil pump is satisfied while satisfying the preset restart condition, the normal engine restart process is performed under cooperative control with the controllers.

That is, the motor controller (P-MCU) of the electric oil pump drives the pump motor at high duty according to a normal control procedure at the time point of restarting the vehicle controller when the pump is in a normal state (see FIG. 3). The pressure will reach the target value.

In addition, the motor controller (I-MCU) that controls the ISG starts driving the ISG to perform engine motoring (ISG motoring control (speed control)), and then the engine rotates so that the engine speed rises to the idle speed. When the engine controller starts the fuel injection to terminate the engine motoring of the ISG, and completes the engine start (S90).

Of course, when the mechanical oil pump reaches an idling speed that can generate sufficient pressure, the driving of the electric oil pump is stopped, and after the engine start is completed, normal fuel injection control is performed by the engine controller.

As a normal restart condition in which the engine is restarted in an idle stop state of the engine, as shown in the example of FIG. If applicable, it may be set to satisfy the restart condition.

On the other hand, if the failure condition (EOP Fail) of the electric oil pump is satisfied while satisfying the restart condition, the restart mode of the pump failure (Restart_EOP_Fail) without entering the existing restart logic in the state of stopping the electric oil pump (Fig. 6 and 7) (S90 '), in which the impact of the ISG is controlled according to the pressure of the transmission hydraulic line (hereinafter, referred to as line pressure), which is a sensing value of the hydraulic sensor, so that the vehicle shock can be prevented. .

More specifically, when a restart request is received from the vehicle controller, restart control in case of a pump failure is performed under the cooperative control of the vehicle controller, the motor controller for controlling the ISG, and the engine controller. First, the motor controller (I-MCU) of the ISG is performed. When the) starts driving the ISG and starts the engine motoring by the ISG, the line pressure starts to be generated by the mechanical oil pump in the transmission.

In the present invention, the rotational speed of the ISG is controlled so that the engine speed is smoothly increased as shown in FIG. 6 while the target line pressure is set from the current engine speed to the friction element tightening pressure P1. .

In this way, the rotation speed of the ISG is controlled to slowly increase the engine speed so that the line pressure rises smoothly to the target line pressure P1.

In general, when the line pressure changes, a hydraulic system such as an accumulator is installed in the transmission valve body, so that a delay time slightly smaller than the flow rate is generated.

Then, when the line pressure, the sensing value of the hydraulic sensor, reaches the target line pressure P1, the IGS motor controller controls the driving of the ISG so that the engine speed is set according to the oil temperature and the shift stage condition. Constantly controlled by the engine motoring to continue (S91).

At this time, the engine speed is kept constant for the set time T1 until the line pressure is stabilized, and the friction elements of the transmission are completely engaged in the state where the engine speed and the line pressure are maintained.

Thereafter, after the set time has elapsed while the line pressure is stabilized, the rotation speed of the ISG is increased again to increase the engine speed to the set idle speed (S92). After the ISG motoring is completed (S93), and the engine motoring by the ISG ends after the fuel injection start (HEV motor speed control continues), the engine restart mode is terminated (S94).

Of course, the line pressure is also increased while the engine speed is increased to the idle speed as described above to reach the line pressure at idle.

After that, the normal engine fuel injection control is performed by the engine controller while the engine restart mode is terminated.

In this way, according to the engine restart control process according to the present invention, the engine restart response may have a slight delay compared to the conventional electric oil pump operation, but can restart the driver because it can prevent the shock in the transmission during restart Discomfort and anxiety caused by heavy shocks can be eliminated, and the engine can be restarted even in the event of a failure of the electric oil pump.

1 is a configuration diagram in which an auxiliary hydraulic system including an electric oil pump in a hybrid vehicle is added to a hydraulic system of an automatic transmission;

2 is a view for explaining a control state of the electric oil pump in a steady state,

3 is a view for explaining the impact phenomenon occurs when the conventional auxiliary hydraulic system failure;

4 is a flowchart illustrating a process of entering an idle stop mode;

5 is a flowchart illustrating an engine restart process according to the present invention;

6 is a diagram showing an engine motoring control state and a line pressure control state according to the engine restarting method of the present invention;

Figure 7 is a flow chart of the engine restart mode when the pump failure according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: mechanical oil pump 20: electric oil pump

Claims (3)

In the engine restart control method for restarting the engine when the electric oil pump failure in the idle stop state of the hybrid vehicle, (a) driving the electric oil pump in the idle stop state, and determining whether the electric oil pump has failed and stopping the driving if the electric oil pump has failed; (b) driving the ISG and starting engine motoring by the ISG when it is determined that the engine restart condition is based on the vehicle information; (c) The rotation of the ISG until the pressure of the hydraulic line in the transmission rises by the operation of the mechanical oil pump in the transmission until the pressure sensing value of the hydraulic sensor installed in the hydraulic line reaches the target line pressure set as the friction element tightening pressure. Controlling the speed to gently increase the engine speed; (d) controlling the driving of the ISG when the sensing value of the hydraulic sensor reaches a target line pressure, thereby maintaining the engine speed constant for a predetermined time; (e) After the set time, increase the rotation speed of the ISG while the friction elements in the transmission are fully engaged, and increase the engine speed to the idle speed.When the engine speed reaches the idle speed, start the fuel injection to start the ISG motor. Completing the ring termination and engine restart; Engine restart control method when the electric oil pump failure of the hybrid vehicle comprising a. The method according to claim 1, In the step (a), the electric oil pump failure of the hybrid vehicle, characterized in that it is determined whether the electric oil pump failure based on the signal of the hydraulic sensor installed in the hydraulic line in the transmission while the electric oil pump is driven during the idle stop. Engine restart control method. The method according to claim 2, The engine restart control method when the electric oil pump failure of the hybrid vehicle, characterized in that for determining the failure of the electric oil pump when the pressure sensing value of the hydraulic sensor is less than the normal line pressure estimate.

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