KR100792922B1 - Engine start control method of hybrid electric vehicles - Google Patents

Abstract

An engine start control method of hybrid electric vehicles is provided to improve a starting power by controlling the amount of fuel injection according to an idle stop maintaining time when an engine is restarted after idle stop. An engine start control method of hybrid electric vehicles includes the steps of: determining whether or not an ECU(Engine Control Unit) is started by an electric motor from electric motor starting information inputted from an HCU(Hybrid Control Unit) at the time of start-up; calculating the final amount of fuel injection by reflecting a start fuel compensation factor set by considering that a start torque is supplemented by the electric motor on a basic fuel amount in a case where an engine is started by the electric motor; and starting the engine by controlling the fuel injection according the final fuel injection amount. The start fuel compensation factor is set to 1.0.

Description

Engine start control method through cooperative control of hybrid electric vehicles {Engine start control method of hybrid electric vehicles}

1 is a schematic diagram showing each device and a controller provided in a hybrid electric vehicle,

2 is a schematic diagram showing an example of a control period cooperative control of a hybrid electric vehicle;

3 is a diagram illustrating a cooperative control and an engine control timing chart at startup and immediately after startup in a hybrid electric vehicle;

4 is a view showing a fuel control algorithm at start-up according to the present invention;

5 is a diagram illustrating an ignition angle control algorithm at startup according to the present invention.

The present invention relates to an engine control method at start-up through cooperative control of a control period of a hybrid electric vehicle, and when starting from the information input from the HCU at start-up, it is determined that the engine is started by the electric motor. The present invention relates to a method of controlling the engine at start-up to reduce fuel consumption and improve fuel efficiency by allowing the engine to be started by applying a basic fuel amount without considering fuel compensation. The present invention also relates to an engine control method at start-up of a hybrid electric vehicle which improves startability by appropriately controlling fuel injection amount according to an idle stop holding time upon restarting after an idle stop.

As is well known, a hybrid electric vehicle is a vehicle using two or more power sources, and generally refers to a hybrid electric vehicle (HEV) driven using an engine and an electric motor.

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

Hybrid electric vehicles are classified into series, parallel, and complex types according to the power transmission method of the vehicle. Soft, middle, and hard types according to the power sharing ratio of the engine and the electric motor. Classified as

Here, the series type is a structure similar to a general electric vehicle, the driving force is obtained from the electric motor, the engine is mounted only for power generation to compensate for the shortcomings of the electric vehicle with a short driving distance.

In addition, the parallel type is based on driving by the engine, and assists the driving force with the electric motor in low speed operation or acceleration during low engine efficiency.

This parallel type improves fuel economy of the entire drive system by utilizing the optimum operating area of the gasoline engine and the electric motor, and improves fuel efficiency by recovering power to the electric motor during braking.

In addition, the type of the electric motor having a smaller capacity than the capacity of the engine is called a soft type hybrid system. In general, the soft hybrid system does not have an electric vehicle (EV) mode in which the vehicle is driven only by the electric motor.

In contrast, in the case of a hard type hybrid system having a large electric motor, an EV mode in which a vehicle is driven by an electric motor at a low speed can be implemented.

Since the efficiency of the engine is lower than the efficiency of the electric motor at the initial start of the hybrid electric vehicle, it is advantageous in terms of fuel efficiency of the vehicle to start the initial start of the vehicle using an efficient electric motor.

On the other hand, Figure 1 is a schematic diagram showing each device and controller provided in the hybrid electric vehicle, as shown in the hybrid electric vehicle is a vehicle controller (Hybrid Control Unit, hereinafter referred to as "HCU") that controls the overall vehicle It is equipped with a controller for each device constituting the system.

For example, an engine controller for controlling the first half of the engine operation (hereinafter referred to as an engine ECU), a motor controller for controlling the first half of the electric motor operation, a transmission controller for controlling the transmission ( Transmission Control Unit (TCU), a battery management system (Battery Management System (BMS)) that controls the operation of the battery, and an air conditioner controller (Full Auto Temperature Controller, FATC) in charge of room temperature control is provided.

These controllers are connected to the high-speed CAN communication line (eg 500kbps) around the HCU, and the upper controller sends commands to the lower controller while exchanging information between the controllers.

As described above, in the hybrid electric vehicle, a plurality of controllers including the HCU as the upper controller perform cooperative control with each other.

2 is a schematic diagram showing an example of control period cooperative control of a hybrid electric vehicle. As shown in this figure, the HCU exchanges information with each controller through CAN communication and also controls subordinate controllers. Engine torque and engine speed information, start key information, throttle / engine temperature (cooling water temperature) information, etc. are received from the engine ECU, and the HCU sends a fuel injection command, an engine stop command, a fuel injection prohibition command to the engine ECU. Electric motor start information, idle stop information, and the like.

In addition, as shown in FIG. 2, the HCU substantially controls the driving of the electric motor through the MCU. In this case, the MCU controls the driving torque and the driving speed of the electric motor as the driving source according to a control signal applied from the HCU, which is the upper controller. It keeps running.

As described above, cooperative control between controllers is very important in a hybrid electric vehicle. Such cooperative control between the controllers is performed in all cases from the start until the user turns off the ignition key.

In particular, there are a myriad of cooperative control ranges such as starting stability, idling stability, oscillation acceleration, deceleration, idle stop, restart, and so on.

Therefore, for cooperative control between such controllers, there must be a certain protocol, and an appropriate control strategy for controlling them is required.

In other words, when the engine is fully determined and the procedure between the controllers and the information is determined in what order, it is possible to achieve the effects of improved fuel economy and output that are to be realized in the hybrid electric vehicle. This, in turn, causes engine coordination and start-up due to differences in the cooperative control sequence and control start time.

However, in the prior art, there was a rather inadequate aspect of controlling the optimal starting state through cooperative control in a hybrid electric vehicle, and thus, an optimum for improving startability and fuel economy by using various information transmitted through CAN communication when starting the vehicle. An engine control method is required.

Therefore, the present invention is invented to solve the above problems, in the case of starting the engine by the electric motor, considering the starting torque assistance by the electric motor is made in consideration of the fuel compensation without applying fuel as it is the engine It is an object of the present invention to provide a method of controlling the engine at start-up, which can improve fuel efficiency by reducing unnecessary fuel consumption.

In addition, an object of the present invention is to provide an engine control method for starting a hybrid electric vehicle that improves startability by appropriately controlling the fuel injection amount according to the idle stop holding time upon restarting after an idle stop.

Another object of the present invention is to provide a method of controlling an engine at the start of a hybrid electric vehicle by controlling the ignition angle at the start of the electric motor so that the rotation speed is not large and thereby improving the riding comfort.

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

The present invention provides an engine control method for starting a hybrid electric vehicle.

Determining whether the engine controller (engine ECU) is started by the electric motor from the electric motor starting information input from the vehicle controller (HCU) at start-up;

Calculating the final fuel injection amount by reflecting the starting fuel compensation coefficient set in the basic fuel amount in consideration of starting torque assistance by the electric motor when it is determined that the engine is in the starting state by the electric motor;

Controlling fuel injection according to the final fuel injection amount to start an engine;

It provides an engine control method at start-up through cooperative control of the control period of the hybrid electric vehicle comprising a.

Here, 1.0 is used as the starting fuel compensation coefficient.

Immediately after starting by the electric motor, the fuel compensation is performed after starting by reflecting the fuel compensation coefficient set according to the coolant temperature, and it is determined that the engine is restarted after the idle stop from the idle stop information input from the vehicle controller. In this case, it is characterized in that the fuel compensation by further reflecting the compensation coefficient according to the previous idle stop holding time.

In addition, the engine control method when starting according to the present invention, if it is determined that the starting state by the electric motor, maintaining the starting ignition angle constant to a specific value determined according to the engine speed, map, cooling water temperature, intake temperature situation It characterized in that it further comprises.

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

3 is a diagram illustrating a cooperative control and engine control timing chart, which shows a general control state at startup and immediately after startup in a hybrid electric vehicle, and shows engine speed (rpm) in an engine controller (hereinafter referred to as an "engine ECU"). ) Shows the control status according to the full-width judgment information judged by) and the electric motor start information and fuel injection permission information inputted through CAN communication from the vehicle controller (hereinafter referred to as "HCU"). .

When the driver operates the ignition key to start, the electric motor is driven first and the engine is started by the electric motor.

In this process, the engine ECU receives electric motor start information and fuel injection permission information from the HCU through CAN communication. The engine speed is increased by driving the electric motor, and then a certain engine speed is reached to reach a full determination. When the engine ECU is started, fuel injection is started at the time of permitting the fuel injection permission information input from the HCU to allow the engine to be started.

After the engine is started, the electric motor is stopped at a certain time point, and then the engine is kept idle according to the idling target rpm, and the idling stabilization correction is performed in the ignition angle control.

In the engine starting process of the hybrid electric vehicle, as shown in FIG. 3, the engine ECU needs to increase the fuel injection amount for starting the engine from the start of fuel injection. In this case, the amount of fuel is reflected by reflecting a preset compensation coefficient according to the cooling water temperature. Will be increased relative to the base fuel level.

However, in the case of a hybrid electric vehicle (starting with an electric motor) as described above, the electric motor continues to be driven for a predetermined time from before fuel injection to after starting, and thus, the electric motor starts at engine start and immediately after starting. Despite assisting torque, fuel injection is unnecessarily increased like existing vehicles, which leads to poor fuel economy.

Therefore, in a hybrid electric vehicle, differentiation is required in the fuel compensation process in the case of starting by an electric motor, distinguished from starting by a starter (only when an abnormality occurs in the electric motor system). In order to solve the fuel economy problem, a fuel control method that reflects a starting fuel compensation process that is not considered in an existing vehicle is proposed.

4 is a diagram illustrating a fuel control algorithm at start-up according to the present invention, wherein the basic fuel amount is a fuel amount preset according to the air flow rate measured by the intake air amount sensor, and the basic fuel amount is calculated according to the measured intake air amount. The final fuel injection amount is calculated by performing fuel amount compensation according to various conditions.

First, when the engine is started by the starter at start-up, after starting the engine ECU, the engine ECU compensates the starting fuel compensation factor by reflecting the preset starting fuel compensation coefficient according to the coolant temperature in the basic fuel amount as usual. As a result, the final fuel injection amount reflecting the starting fuel compensation coefficient is calculated to allow the engine to be started by the final fuel injection amount.

Here, the fuel injection amount should be increased to start the engine, and the preset starting fuel compensation coefficient is greater than 1.0 (for example, 3.0, 2.8, ...) according to the coolant temperature. Compensation is performed so that the fuel amount is increased by the fuel compensation factor to increase the fuel amount from the basic fuel amount.

On the other hand, when it is determined that the engine is started by the electric motor from the electric motor start information input through the HCU from the CAN communication at start-up, the starting fuel compensation factor is reflected to 1.0, and thus the basic fuel amount is applied without any fuel compensation. To start the engine.

In the case of starting by the electric motor as shown in Figure 3, since the electric motor continues to drive for a predetermined time from before the fuel injection to after the start to assist the starting torque, it is not necessary to increase the fuel injection amount, even if no additional starting fuel compensation Engine start is possible.

As a result, unnecessary fuel increase at start-up is eliminated, thereby improving fuel economy.

On the other hand, immediately after the start-up is started by the starter motor, the fuel compensation after the start is performed by reflecting the pre-started fuel compensation coefficient according to the cooling water temperature as in the usual case after the slow-down determination. The final fuel injection amount, which reflects the coefficient, is calculated so that the engine is driven by this final fuel injection amount.

On the other hand, immediately after the start-up by the electric motor is performed after the start-up fuel compensation by reflecting the additional after-start fuel compensation coefficient set according to the coolant temperature after the determination of the full width and the fuel injection permission from the HCU, In addition, if it is determined that restart is performed after the idle stop from the idle stop information input from the HCU, the fuel compensation is performed after the start by additionally reflecting the compensation coefficient according to the previous idle stop holding time.

That is, when it is determined that the restart after the idle stop immediately after the start is started by the electric motor as shown in Figure 4 by multiplying the compensation coefficient according to the idle stop holding time by the preset compensation coefficient according to the coolant temperature to determine the fuel compensation factor after starting It calculates and calculates the final fuel injection amount reflecting the fuel compensation coefficient after the start so that the engine is driven by this final fuel injection amount.

In this way, the fuel injection amount is increased / decreased according to the idle stop holding time to improve startability. The fuel injection amount is increased to improve restart conditions when the previous idle stop time is long to reflect the idle stop holding time. This improves the startability.

On the other hand, in the present invention to improve the ignition angle control process during start-up, Figure 5 is a view showing the ignition angle control algorithm at start-up according to the present invention.

As shown in FIG. 5, the basic ignition angle is determined by reflecting the engine speed (rpm), cooling water temperature, intake air temperature, knocking correction, and the like.

Conventionally, the engine start condition is optimized due to the change in the ignition angle and the perception of the ignition angle. However, in the present invention, the change in the ignition angle is kept constant at the start condition when the electric motor is started in the hybrid electric vehicle. Control so that the rotational speed change vibration is reduced during the start control.

In more detail, first, after the full-width determination and fuel injection permission from the HCU, the starting ignition angle according to the engine speed (rpm), cooling water temperature, and intake temperature, when the engine is started by the starting motor at the start. And the engine is started by this starting ignition angle.

On the other hand, when it is determined that the engine is started by the electric motor based on the electric motor start information input from the HCU through CAN communication at start-up, the start ignition angle is a start condition according to the engine speed, map, cooling water temperature, and intake temperature. Start-up control is performed so that it remains constant at a certain set value.

That is, in the case of starting the electric motor is to control the ignition angle does not change.

As described above, in the present invention, by controlling the ignition angle to be kept constant at the start, the variation in the number of revolutions is not large, thereby improving the riding comfort.

As described above, in the engine control method of the hybrid electric vehicle according to the present invention, when it is determined that the engine is started by the electric motor from the information input from the HCU at the start, the starting torque assistance by the electric motor is considered. Therefore, by starting the engine by applying the basic amount of fuel as it is without compensating for fuel, unnecessary fuel consumption can be reduced and fuel efficiency can be improved.

In addition, the startability can be improved by controlling the fuel injection amount according to the idle stop holding time upon restarting after the idle stop.

In addition, by controlling the ignition angle to be kept constant at the start of the electric motor, it is possible to minimize the variation in the number of revolutions, thereby improving the riding comfort.

Claims (4)

In the engine control method at the start of the hybrid electric vehicle, Determining whether the engine controller (engine ECU) is started by the electric motor from the electric motor starting information input from the vehicle controller (HCU) at start-up; Calculating the final fuel injection amount by reflecting the starting fuel compensation coefficient set in the basic fuel amount in consideration of starting torque assistance by the electric motor when it is determined that the engine is in the starting state by the electric motor; Controlling fuel injection according to the final fuel injection amount to start an engine; Engine control method at start-up through cooperative control of the control period of the hybrid electric vehicle comprising a. The method according to claim 1, The engine control method at start-up through the control period cooperative control of a hybrid electric vehicle, characterized by using 1.0 as the starting fuel compensation coefficient. The method according to claim 1, Immediately after starting by the electric motor, the fuel compensation is performed after starting by reflecting the preset fuel compensation coefficient according to the coolant temperature.If it is determined that the engine is restarted after the idling stop from the idling information input from the vehicle controller, A method of controlling an engine at start-up through cooperative control of a control period of a hybrid electric vehicle, characterized in that the fuel compensation is further reflected by a compensation factor according to the idle stop holding time. The method according to claim 1 If it is determined that the electric motor is in the starting state, the step of maintaining the starting ignition angle to a specific value determined according to the engine speed, map, cooling water temperature, intake air temperature conditions of the hybrid electric vehicle further comprising Control period Engine control method at start-up through cooperative control.

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