KR20100033892A - Method for reducing exhaust gas of hard type hybrid electric vehicle - Google Patents

Abstract

PURPOSE: An exhaust gas decrease method of a hard type hybrid vehicle is provided to improve the performance by the activation of a cam by controlling a cam before emitting fuel using an ISG. CONSTITUTION: A first starting is detected in an engine. After the first starting, fuel is emitted. An intake cam is activated before emitting fuel. When the intake cam is activated, a valve overlap is formed. When the intake cam is activated, the engine is rotated using an ISG(Integrated Starter Generator) in order to make fluid pressure higher than a reference value. An OCV(Oil Control Solenoid Valve) is operated in order to operate the intake cam and to control the fluid pressure.

Description

Method for reducing exhaust gas of hard type hybrid electric vehicle}

The present invention relates to a method for reducing the exhaust gas of a hard type hybrid vehicle, and more particularly, to activate the intake cam of the engine oil pressure using the ISG to reduce the amount of exhaust gas generated at the front end of the catalyst during cold start of the engine in the hybrid vehicle. The present invention relates to a method for reducing exhaust gas of a hard-type hybrid vehicle, which is configured to form a valve overlap and forms a valve overlap by appropriately advancing an intake cam to smoothly promote vaporization of fuel to ensure combustion stability.

Recently, various technologies for reducing the exhaust gas have been tried in response to the demand for improving vehicle fuel economy and developing more environmentally friendly products.

In the case of gasoline vehicles, the following technologies are applied to satisfy SULEV (Super Ultra Low Emission Vehicle), which is the most stringent emission regulation.

1) Tumble flow is formed by installing VCM (Variable Charge Motion) on the intake side to mix fuel and air smoothly.

2) Change the injector hole from 4 holes to 12 holes to mix fuel and air smoothly.

3) Long Rich & Iridium Spark Plugs are used to facilitate combustion inside the engine.

4) engine O ₂ sensor heating and application of the linear lambda (Linear Lambda) sensor as the front portion O ₂ sensor for accurate lambda control in order to speed up the feedback control lambda (Lambda) after start-up.

5) Secondary Air Injection is applied to the exhaust side to reduce the HC and CO, which are carbon components in the exhaust gas.

6) Apply a warm-up catalyst converter (WCC) and an under-floor catalyst converter (UCC) as a catalyst for the post-treatment process to purify the exhaust gas, and increase the cell density of the catalyst to increase the reaction area when purifying exhaust gas. And the amount of precious metals is increased to increase the amount of exhaust gas purification.

7) Maintain exhaust pipe temperature by double designing exhaust pipe.

8) Fast Catalyst Heating is applied to suppress the exhaust gas and increase the catalyst purification efficiency quickly.

9) Lean control of the lambda value in order to reduce HC exhaust gas generated during catalyst heating.

In this way, various technologies applicable to gasoline vehicles can be used to satisfy the North American SULEV regulations.However, among the above technologies, the technology of 1) to 7) raises vehicle costs due to the improvement of hardware. 9) Technology has a problem based on software improvement or hardware improvement.

In order to reduce the exhaust gas before the catalyst is activated in the gasoline vehicle, in addition to the above-described method, the temperature of the intake port must be increased immediately after the FTP cold start to facilitate vaporization of the fuel, thereby ensuring the same combustion stability with a lower fuel injection amount.

Therefore, in the case of gasoline vehicles, in the single CVVT (Continuously Variable Valve Timing), in which only the intake cam is operated variably after the engine starts, or in the dual CVVT in which both the intake / exhaust cams operate variably, When the cam operation is possible, overlap of valves are formed, and hot combustion gas increases the temperature of the intake port during cam phasing in the idle state immediately after the vehicle start (cold start) to promote vaporization of fuel. The same combustion stability can be ensured with a small amount of fuel.

In other words, if the cam paging is optimized immediately after the cold start, the fuel injection amount can be reduced, thereby reducing HC exhaust gas in this section.

However, in the case of gasoline vehicles, in order to operate the cam, it takes time to generate the hydraulic pressure to activate the cam after starting the engine. In order to operate, CVVT can normally be operated after at least 3 seconds after starting the engine.

That is, in gasoline vehicles, the effect of valve overlap cannot be obtained during the time when the cam operation is impossible after cold start of the engine, and there is no way to move the cam without using hardware without the hydraulic pressure for cam operation being activated. There is.

Thus, since the gasoline vehicle is before the hydraulic pressure for the cam operation is formed in the engine cold state, even if the specification of the catalyst is increased to reduce the exhaust gas, the catalyst is also inactive, so the effect is insignificant.

As described above, a lot of efforts have been made to reduce exhaust gas in gasoline vehicles, but since HC at the front end of the catalyst which occurs immediately before the catalyst is activated after cold start of the engine is difficult to be purified by the catalyst, separate hardware (for example, VCM) Equipped with a lamp to reduce the amount of HC generated after the first engine start.

In the case of a hybrid vehicle, the same target as the gasoline vehicle, SULEV, which is a North American exhaust gas regulation, is aimed at improving the merchandise.

Engine running time during FTP driving is 50% to 60% for hard type hybrid vehicles and 70 to 80% for soft type hybrid vehicles. For example, the amount of exhaust gas generated from the engine is less in the front of the catalyst than in the gasoline vehicle of the same class, but the amount of exhaust gas emitted after the catalyst is activated by purifying and exhausting the exhaust gas at the rear of the catalyst is a gasoline vehicle or a hybrid vehicle. It doesn't make much difference.

FIG. 1 is a graph showing the cumulative HC amount of a hybrid vehicle during the FTP 75 mode driving in the exhaust gas test mode, and the HC amount exhausted during the FTP driving of the hybrid vehicle is about 0.14 g / s before the catalyst is activated (about 20 seconds). It can be seen that about 80% of the amount of HC generated is generated.

FIG. 2 is a graph showing HC concentrations of catalysts before and after catalysts at the beginning of the FTP 75 mode driving of the hybrid vehicle. It can be seen that the concentration of HC is increased again when the catalyst is heated in the heating section and then out of the catalyst heating section.

In the case of the rear stage of the catalyst, the HC produced at the front end of the catalyst cannot be purified until the catalyst is activated. After the heating of the catalyst, the concentration of HC starts to decrease. After the completion of the catalyst heating, the catalyst is sufficiently purified even if the concentration of HC is high at the front of the catalyst. As a result, it can be confirmed that the exhaust gas of HC hardly occurs at the rear end of the catalyst.

Therefore, it can be seen that reducing the concentration of hydrocarbons generated at the front end of the catalyst after the engine is started and before the catalyst is activated plays a significant role in reducing the amount of exhaust gas.

However, there is a problem that it is difficult to purify the hydrocarbon with the catalyst before the catalyst is activated after the cold start of the engine.

The present invention has been invented to solve the above problems, in the hard type hybrid vehicle to reduce the amount of exhaust gas generated at the front end of the catalyst before the catalyst is activated after the engine cold start engine oil pressure by using the ISG cam Provides a method for reducing the exhaust gas of a hard type hybrid vehicle, which is formed above a reference value that can be activated, and then operates OCV to advance the intake cam to a target value, thereby rapidly inhaling the fuel to facilitate vaporization of fuel to secure combustion stability. Its purpose is to.

In order to achieve the above object, the present invention provides a method for reducing the exhaust gas at the front end of the catalyst before the catalyst activation after the first cold start of the engine in a hard type hybrid vehicle,

Determining whether the engine is first started in cold engine; Determining whether fuel injection is performed after the first start in cold engine; Activating the intake cam before fuel is injected; When the intake cam is activated by advancing to form a proper valve overlap provides a method for reducing the exhaust gas of a hard type hybrid vehicle comprising a.

Here, the step of activating the intake cam, characterized in that for forming a hydraulic pressure of more than a set value by rotating the engine using the ISG,

Preferably, in order to advance the intake cam is characterized in that to operate the OCV to control the hydraulic pressure.

In addition, preferably, the step of determining whether the engine is started for the first time is characterized in that it comprises the step of comparing the number of engine startup with the set number of times, and determining whether the coolant temperature is lower than the set temperature.

Exhaust gas reduction method of the hard type hybrid vehicle according to the present invention has the advantage that the exhaust gas reduction is more efficient than the gasoline vehicle without adding additional hardware at the first start of the engine,

Specifications for catalysts, exhaust gas aftertreatment systems, and specifications for VCM or 12-hole injectors for SULEV emission regulation can be omitted.

In addition, by using catalysts and four-hole injectors, which are less expensive than those for gasoline vehicles, and by eliminating VCM, North American SULEV regulations can be met.

When the engine is rotated using ISG, cam control can be performed even before fuel injection, thereby improving performance by cam activation.

In addition, the present invention is by reducing the exhaust gas can be effectively expanded the promotion of the country in the strict emission standards, such as the United States by increasing the marketability to further meet the SULEV emission standards in North America.

In addition, it can be expected to be immediately implemented by cooperative control of HCU and ECU.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. In the description, overlapping descriptions of the same parts as the related art may be omitted.

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

In order to reduce the amount of exhaust gas generated at the front end of the catalyst before the catalyst is activated after the first start of the engine in the hard type hybrid vehicle, the intake air is injected before fuel is injected by activating the intake cam using an integrated starter generator (ISG). Advance the cam to the target to promote vaporization of the fuel to make it smoother.

FIG. 3 is a schematic system configuration diagram of a hard type hybrid vehicle equipped with an engine clutch, and FIG. 4 is a control flowchart for advancing an intake cam of the hard type hybrid vehicle according to the present invention.

As shown in FIG. 3, the hard type hybrid vehicle includes an engine as a main power source and a motor as an auxiliary power source, an ISG configured to rotate the engine during engine cold start and restart, and is configured between the engine and the motor. Opening the engine clutch (open) is made of a structure capable of driving EV (Electric Vehicle) mode to drive the vehicle with only the motor.

The hybrid vehicle is equipped with a vehicle controller (Hybrid Control Unit, hereinafter referred to as "HCU") that controls the overall vehicle, and has a controller for each device constituting the system.

For example, an engine control unit (ECU), which controls the first half of the engine operation, a motor control unit (MCU) controlling the first half of the electric motor operation, a transmission controller (Transmission) controlling the transmission The control unit (TCU), a battery management system (Battery Management System (BMS)) for controlling the operation of the battery, the air conditioning controller (Full Auto Temperature Controller, FATC) in charge of room temperature control is provided.

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

That is, in a hybrid vehicle, a plurality of controllers including the HCU as the upper controller perform cooperative control with each other.

In such hybrid vehicles, the engine speed can be increased to several hundred rpm by using ISG before fuel is injected at the first start of the engine. Therefore, when the engine is rotated at a set value (for example, 1000 rpm or more) for a predetermined time (about 2 to 3 seconds) by using the ISG at the first start of the engine, the engine generates hydraulic pressure above the target value and activates the cam.

Here, the cam activation means that the intake or exhaust side cam of the engine can be operated. Normally, the engine oil pressure must be higher than or equal to the set pressure (for example, 1 bar and 1000 rpm). Depending on the temperature conditions, it must pass more than a certain time.

When the engine is rotated using the ISG, the engine oil temperature is increased, and after a predetermined time according to the rising oil temperature, the oil pressure increases and the intake cam is operably activated.

The ECU then controls the oil pressure to advance the intake cam to the target by operating an oil control solenoid valve (OCV) to operate the intake cam. When the intake cam is advanced and the valve overlap is properly formed, the ECU injects fuel according to the fuel injection command of the HCU to ignite the engine.

As described above, in a hard type hybrid vehicle, the cam is operated first using the ISG, and then a fuel injection command is sent from the HCU to the ECU to ignite the engine.

1. The engine's actual compression ratio is increased by advancing the intake cam before the ECU injects fuel, so when the explosion is caused by the first fuel injection, it is possible to induce complete combustion by increasing the compression ratio inside the engine cylinder. The same combustion safety can be secured.

2. Even when the engine is started for the first time, the intake cam is advanced to reduce exhaust gas by valve overlap.

3. When the engine is started for the first time, before the fuel is injected, ISG power assistance is used to control the engine RPM above the reference value to enable fuel injection with sufficient engine negative pressure to reduce the amount of inlet wall wetting. It is possible to reduce the exhaust gas.

5 is a graph showing the HC exhaust gas concentration at the front end of the catalyst with or without the application of the intake cam advance logic according to the present invention.

In fact, when ISG is used in a hard type hybrid vehicle, as shown in FIG. 5, the gradient of the concentration of HC exhaust gas at the front end of the catalyst and the time at which the maximum value occurs vary depending on whether the cam is advanced or not. After about 3 seconds after starting, the angle of valve overlap due to cam advance is different so that the amount of HC exhaust gas at the front end of the catalyst is different.

That is, as shown in FIG. 5, since the concentration of exhaust gas at the front end of the catalyst generated before the catalyst activation (catalyst heating) has a great influence on the amount of generated exhaust gas, the intake cam is advanced immediately before the fuel is injected after the engine is started. During the catalyst heating section (approximately 20 seconds), a difference occurs in the HC exhaust gas at the front end of the catalyst depending on the valve overlap angle due to the cam advancing. Therefore, when the cam is advanced by using the ISG according to the present invention, the exhaust gas at the front end of the catalyst It can be seen that the concentration gradient is more gentle and the maximum value occurs later to reduce the amount of exhaust gas.

6 is a graph illustrating an intake cam operation time and a valve overlap angle of a hybrid vehicle not applying the cam advance logic according to the present invention, and FIG. 7 is an intake cam operation time of the hybrid vehicle to which the cam advance logic is applied according to the present invention; A graph showing the valve overlap angle.

In the case of FIG. 6, the fuel injection is performed immediately after starting the engine, indicating that the cam advance may be performed only after a time for activating the cam after starting the engine. In the case of FIG. By forming a hydraulic pressure in the cam to activate the intake cam, the intake cam is operated to advance to the desired position to form an appropriate valve overlap, thereby instructing the ECU to inject fuel at the command of the HCU.

As can be seen in Figures 6 and 7, by increasing the intake rate by advancing the intake cam before the fuel is injected by using the ISG during the engine cold start, it is possible to reduce the exhaust gas of the front end of the catalyst before the catalyst is activated.

As described above, the control is performed by the plurality of controllers including the HCU through cooperative control.

Hereinafter, the control operation for reducing the exhaust gas according to the present invention is summarized as follows.

After cold start, the ISG is used to idle the engine until the engine's intake cam is operational after the initial start-up of the cold engine of the hard type hybrid vehicle.

When sufficient oil pressure is formed by idling the engine and the intake cam is enabled, the EMS (Engine Management System) ECU recognizes the activation of the intake cam and operates the OCV to operate the intake cam. Control to advance to the target position, and transmits the intake cam advance complete signal to the HCU.

The HCU sends a fuel injection command to the EMS ECU after receiving the intake cam advance completion signal, and the ECU injects fuel.In this case, the valve overlap is optimized according to the advance of the intake cam. The gasification of the gas is accelerated to allow complete combustion.

Accordingly, unburned gas is reduced and the amount of exhaust gas emitted is also reduced.

In such a control operation, the cooling water temperature is compared with the set value to determine whether the engine is cold started.

1 is a graph showing the cumulative HC amount of the hybrid vehicle when the FTP 75 mode driving exhaust gas test mode,

FIG. 2 is a graph showing HC concentrations of catalysts before and after catalysts at the beginning of FTP 75 mode driving of a hybrid vehicle; FIG.

3 is a schematic system configuration diagram of a hard type hybrid vehicle equipped with an engine clutch;

4 is a control flowchart for advancing an intake cam of a hard type hybrid vehicle according to the present invention;

5 is a graph showing the HC exhaust gas concentration at the front end of the catalyst with or without the application of intake cam advance logic according to the present invention;

6 is a graph showing the intake cam operation time and the valve overlap angle of the hybrid vehicle without applying the cam advance logic according to the present invention;

7 is a graph showing the intake cam operation time and the valve overlap angle of the hybrid vehicle to which the cam advance logic according to the present invention is applied.

Claims (4)

As a method for reducing the exhaust gas at the front end of the catalyst in the hard type hybrid vehicle before the catalyst activation after the initial cold start of the engine, Determining whether the engine is first started in cold engine; Determining whether fuel injection is performed after the first start in cold engine; Activating the intake cam before fuel is injected; Advancing when the intake cam is activated to form an appropriate valve overlap; Exhaust gas reduction method of a hard type hybrid vehicle, characterized in that comprises a. The method according to claim 1, Activating the intake cam, A method of reducing exhaust gas of a hard type hybrid vehicle, wherein the engine is rotated using the ISG to generate a hydraulic pressure equal to or higher than a set value. The method according to claim 1, The method of reducing the exhaust gas of a hard type hybrid vehicle, characterized in that for controlling the hydraulic pressure by operating the OCV to advance the intake cam. The method according to claim 1, The step of determining whether the engine is the first start in cold, Comprising the step of comparing the number of engine start with the set number, and determining whether the cooling water temperature is below the set temperature.

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