KR102365178B1 - Exhaust system of turbo gasoline direct injection engine and control method thereof - Google Patents

Abstract

The present invention relates to an exhaust system for a direct injection gasoline turbo engine capable of increasing the fuel cut section and shortening the LOT arrival time at the initial stage of start-up, and a method for controlling the same. The exhaust system includes a direct injection gasoline turbo engine; secondary air supply means for supplying secondary air to the exhaust gas exhausted from the engine; a warm-up catalytic converter (WCC) installed downstream from the point where the secondary air supply means is connected and into which exhaust gas is introduced; It includes a fuel cut nox strap (FCNT) installed downstream of the warm-up catalytic converter to collect NOx in the fuel cut section and purify NOx by using a reducing agent in the acceleration section.

Description

EXHAUST SYSTEM OF TURBO GASOLINE DIRECT INJECTION ENGINE AND CONTROL METHOD THEREOF

The present invention relates to an exhaust system for a direct-injection gasoline turbo engine and a control method therefor, and more particularly, to an exhaust system for a direct-injection gasoline turbo engine capable of increasing the fuel cut section and shortening the LOT arrival time at the initial stage of start-up and the same It relates to a control method.

In general, a gasoline engine is a device that uses, as a power, the power of an explosion generated by igniting gasoline mixed with air through ignition in a cylinder.

As for such a gasoline engine, an engine having improved power and fuel efficiency has been continuously developed and used.

For example, a lean-burn engine with a mixture mass ratio superior to that of a general gasoline engine was developed, and engine performance was further improved, such as a Gasoline Direct Injection engine (GDI engine) having a mixture mass ratio superior to that of the lean-burn engine was developed. became Recently, a turbo gasoline direct injection engine (T-GDI engine) has been developed for the purpose of downsizing the engine.

In general, the catalyst of the T-GDI engine has a slower time to reach the catalyst activation temperature (Light Off Time; LOT) than the GDI engine or the MPI engine. This is a characteristic of the T-GDI engine, and the cause is that the time at which the catalyst temperature reaches LOT is naturally delayed due to heat loss generated while exhaust gas passes through the turbocharger.

In addition, the T-GDI engine applies a high-flow injector for high performance. As this high-flow injector was applied, it was difficult to precisely control the control of the fuel injection amount compared to the GDI engine or the MPI engine in the low-load region at the beginning of the startup, and this caused a lot of initial RAW E/M. .

And, due to the characteristics of the T-GDI engine, it was a very difficult task to respond to the emission gas regulation (SULEV) in the T-GDI engine. Active Catalyst Heating strategy is being used to shorten LOT. However, this response has a problem that acts as a factor that deteriorates fuel efficiency.

Registered Patent 10-1551017 (2015. 09. 01)

The present invention provides an exhaust system for a direct-injection gasoline turbo engine capable of improving fuel efficiency while responding to emission gas regulations by increasing the fuel cut section and reducing the LOT arrival time at the initial stage of start-up, and a method for controlling the same.

An exhaust system of a direct injection gasoline turbo engine according to an embodiment of the present invention includes: a direct injection gasoline turbo engine; secondary air supply means for supplying secondary air to the exhaust gas exhausted from the engine; a warm-up catalytic converter (WCC) installed downstream from the point where the secondary air supply means is connected and into which exhaust gas is introduced; It includes a fuel cut nox strap (FCNT) installed downstream of the warm-up catalytic converter to collect NOx in the fuel cut section and purify NOx by using a reducing agent in the acceleration section.

a front-end oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter; a stopped oxygen sensor for detecting the oxygen concentration of the exhaust gas passing through the warm-up catalytic converter; It may further include a rear-end oxygen sensor for detecting the oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter.

a three-way catalyst (TWC) installed downstream of the Fuel Cut Nox Strap to purify harmful substances in exhaust gas discharged from the Fuel Cut Nox Strap; a front-end oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter; It may further include a rear-end oxygen sensor for detecting the oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter.

a hydrocarbon trap (HC TRAP) installed downstream of the fuel cut nox strap to adsorb hydrocarbons in the exhaust gas discharged from the fuel cut nox strap; a three-way catalyst (TWC) installed downstream of the Fuel Cut Nox Strap to purify harmful substances in the exhaust gas discharged from the Fuel Cut Nox Strap; a front-end oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter; It may further include a rear-end oxygen sensor for detecting the oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter.

On the other hand, the control method of the exhaust system of the direct injection gasoline turbo engine according to an embodiment of the present invention includes a first checking step of determining whether the catalyst temperature of the NOx purification means reaches the catalyst activation temperature (LOT) after starting; a secondary air supply step of increasing the temperature of the exhaust gas by supplying secondary air to the exhaust gas, which is performed when the temperature of the catalyst does not reach the catalyst activation temperature (LOT) in the first checking step; a second checking step of determining whether a fuel cut section is performed when the temperature of the catalyst reaches the catalyst activation temperature (LOT) in the first checking step; It is carried out when it is determined that it is not the fuel cut section in the second confirmation step, detects the oxygen concentration of the exhaust gas that is passing or has passed through the warm-up catalytic converter (WCC), and compares the detected value with the lambda value to control rich Or a general control step of performing Lean control; It is carried out when it is determined that it is a fuel cut section in the second confirmation step, and after applying the fuel cut, the oxygen concentration of the exhaust gas that has passed through the warm-up catalytic converter (WCC) is detected, and the detected value and the lambda value are compared. In the Rich state, fuel cut is continuously applied, and in the Lean state, the fuel cut control step is stopped.

In the fuel cut control step, after stopping the fuel cut, NOx contained in the exhaust gas is collected through a fuel cut noxtrap (FCNT), the oxygen concentration of the exhaust gas in which the NOx is collected is detected, and the detection value and the lambda value are obtained. By comparison, it further includes the process of applying fuel cut if it is in a rich state, and stopping fuel cut if it is in a lean state.

According to the embodiment of the present invention, it is possible to achieve the effect of improving fuel efficiency while responding to SELEV by increasing the fuel cut section during operation while responding to emission gas regulations by shortening the LOT arrival time at the beginning of the start-up.

In addition, by supplying secondary air to the exhaust gas at the initial stage of start-up, excessive ignition timing retardation can be eliminated, thereby ensuring combustion stability.

And it can be expected that it will be advantageous in terms of back pressure by preventing the application of an excessive number of cells (900 cells) like competitors due to the rapid LOT arrival due to the application of secondary air.

1 is a block diagram showing an exhaust system of a direct injection gasoline turbo engine according to a first embodiment of the present invention;
2 is a block diagram showing an exhaust system of a direct injection gasoline turbo engine according to a second embodiment of the present invention;
3 is a block diagram showing an exhaust system of a direct injection gasoline turbo engine according to a third embodiment of the present invention;
4 is a flowchart illustrating a method for controlling an exhaust system of a direct injection gasoline turbo engine according to the present invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only these embodiments allow the disclosure of the present invention to be complete, and the scope of the invention to those of ordinary skill in the art completely It is provided to inform you. In the drawings, like reference numerals refer to like elements.

1 is a block diagram showing an exhaust system of a direct injection gasoline turbo engine according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing an exhaust system of a direct injection gasoline turbo engine according to a second exemplary embodiment of the present invention. 3 is a block diagram showing an exhaust system of a direct injection gasoline turbo engine according to a third embodiment of the present invention.

1 to 3, the exhaust system of the direct injection gasoline turbo engine according to the embodiment of the present invention includes: a direct injection gasoline turbo engine 10; secondary air supply means 40 for supplying secondary air to the exhaust gas exhausted from the engine 10; a warm-up catalytic converter (20, WCC) installed downstream from the point where the secondary air supply means (40) is connected and into which exhaust gas is introduced; It is installed downstream of the warm-up catalytic converter 20 and collects NOx in the fuel cut section, and uses a reducing agent in the acceleration section to purify NOx.

A direct injection gasoline turbo engine (10; hereinafter referred to as 'engine') is an engine in which a direct injection gasoline engine (Gasoline Direct Injection engine, GDI engine) is equipped with a turbocharger to compress and supply air supplied to the engine. means

The secondary air supply means 40 serves to supply secondary air to the exhaust gas exhausted from the engine 10 to increase the temperature of the exhaust gas through post-combustion. Here, the secondary air supply means 40 may be implemented in various ways, for example, including an air tank in which secondary air is stored, and a nozzle for supplying secondary air of the air tank into an exhaust line through which exhaust gas flows. can be implemented. Of course, the secondary air supply means is not limited to the presented embodiment and may be implemented in various ways to supply secondary air to exhaust gas exhausted from the engine.

A warm-up catalytic converter (20, WCC) is installed downstream from the point where the secondary air supply means is connected, and mainly purifies the exhaust gas discharged before the engine warms up.

In this way, as the secondary air supply means 40 and the warm-up catalytic converter 20 are sequentially exhausted, the catalyst activation temperature (Light Off Time; LOT) of the catalyst included in the warm-up catalytic converter 20 through a post-combustion reaction of fuel can be shortened, and the catalyst heating (CH) can be reduced or omitted at the initial stage of start-up.

A fuel cut nox trap (30, Fuel Cut Nox Trap; FCNT) is installed downstream of the warm-up catalytic converter 20 to collect NOx in the fuel cut section and purify NOx by using a reducing agent in the acceleration section is a means to Accordingly, it is possible to increase the fuel cut section by reducing the amount of NOx generated.

The reason why the fuel cut nox strap 30 is applied in the present invention is because there is a problem in that a large amount of NOx is discharged immediately after the fuel cut (Feul Cut). As a side note, there is no combustion in the Feul Cut, so NOx is emitted. However, right after the end of the fuel cut, the engine proceeds with rich combustion, but since the catalyst is in an oxidizing atmosphere, NOx is not purified and is simply discharged.

Accordingly, the fuel cut nox trap 30 is a conventional under-floor catalytic converter (UCC) with a stored NOx reduction catalyst (Lean NOx Trap; LNT) of a diesel engine. Components (Pt, Ba, etc.) ), which is a means to which NOx storage performance is added.

The fuel cut nox strap 30 does not require separate control logic such as NOx regeneration logic and desulfurization logic for desorbing NOx from LNT of a conventional diesel engine or ultra-lean GDI engine. The reason for this is that the NOx occluded/purified immediately after the fuel cut applied in the present invention is at a low level, and thus the occlusion amount is small.

On the other hand, the present invention arranges oxygen sensors 50a, 50b, 50c for detecting the oxygen concentration of exhaust gas at various points for system control, and additionally purifies harmful substances discharged from the fuel cut nox strap 30. It may further include means.

For example, in the exhaust system of a direct injection gasoline turbo engine according to the first embodiment of the present invention, as shown in FIG. 1 , a front-end oxygen sensor ( 50a) and; a stop oxygen sensor (50b) for detecting the oxygen concentration of the exhaust gas passing through the warm-up catalytic converter (20); It further includes a rear-end oxygen sensor (50c) for detecting the oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter (20).

At this time, the front end oxygen sensor 50a, the intermediate oxygen sensor 50b and the rear end oxygen sensor 50c are means for detecting the oxygen concentration in the exhaust gas, and their installation positions are changed. Therefore, the air-fuel ratio is calculated by comparing the oxygen concentration in the exhaust gas measured by the front-end oxygen sensor 50a with the oxygen concentration in the exhaust gas measured by the intermediate oxygen sensor 50b or the rear-end oxygen sensor 50c.

In addition, the exhaust system of the direct injection gasoline turbo engine according to the second embodiment of the present invention is installed downstream of the fuel cut knock strap 30 as shown in FIG. 2 and is discharged from the fuel cut knock strap 30. a three-way catalyst (60, TWC) for purifying harmful substances in exhaust gas; a front-end oxygen sensor (50a) for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter (20); It further includes a rear oxygen sensor 50c for detecting the oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter 20.

Here, the three-way catalyst (60, Three Way Catalyst; TWC) is a means for purifying by further reducing NOx as well as oxidizing CO or HC contained in exhaust gas.

And the exhaust system of the direct injection type gasoline turbo engine according to the third embodiment of the present invention is installed downstream of the fuel cut knock strap 30 as shown in FIG. 3 and the exhaust discharged from the fuel cut knock strap 30 a hydrocarbon trap (HC TRAP) for adsorbing hydrocarbons in the gas; a three-way catalyst (TWC) installed downstream of the Fuel Cut Nox Strap to purify harmful substances in the exhaust gas discharged from the Fuel Cut Nox Strap; a front-end oxygen sensor (50a) for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter (20); It further includes a rear oxygen sensor 50c for detecting the oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter 20. In the drawing, a combination of a hydrocarbon trap (HC TRAP) and a three-way catalyst (TWC) is indicated by reference numeral '70'.

Here, the hydrocarbon trap (HC TRAP) is a means for occluding hydrocarbons (HC) generated during the initial start-up and after the LOT is achieved.

A method of controlling the exhaust system of the direct injection gasoline turbo engine according to the present invention configured as described above will be described.

4 is a flowchart illustrating a method for controlling an exhaust system of a direct injection gasoline turbo engine according to the present invention.

As shown in FIG. 4, in the method for controlling the exhaust system of a direct injection gasoline turbo engine according to the present invention, the catalyst temperature of the NOx purification means, that is, the warm-up catalytic converter 20, WCC, is adjusted to the catalyst activation temperature (LOT) after starting. Determining whether it has been reached (1st confirmation step)

Therefore, when the temperature of the catalyst does not reach the catalyst activation temperature (LOT), secondary air is supplied to the exhaust gas to increase the temperature of the exhaust gas by post-combustion to shorten the time for the catalyst to reach the LOT.

So, when the catalyst temperature reaches the catalyst activation temperature (LOT), it is determined whether it is a fuel cut section. (Second confirmation step)

When it is determined that the fuel cut section is not the fuel cut section according to the judgment in the second confirmation step, the oxygen concentration of the exhaust gas passing through the warm-up catalytic converter 20 is detected using the stop oxygen sensor 50b or the rear oxygen sensor 50c ) and compare the detected value with the lambda value to perform rich control or lean control. (general control stage)

When it is determined that it is a fuel cut section according to the determination in the second confirmation step, the fuel cut is applied.

While applying the fuel cut, the oxygen concentration of the exhaust gas that has passed through the warm-up catalytic converter 20 is detected by the oxygen sensor 50c at the rear end, and the detected value and the lambda value are compared. If this is the case, fuel cut is stopped. (Fuel cut control stage)

Meanwhile, in the fuel cut control step, after stopping the fuel cut, NOx contained in the exhaust gas is collected through a fuel cut noxtrap (FCNT), the oxygen concentration of the exhaust gas in which the NOx is collected is detected, and the detection value and the lambda Comparing the values, if it is in the Rich state, it applies the fuelcut, and if it is in the Lean state, it further includes the process of stopping the fuelcut.

Although the present invention has been described with reference to the accompanying drawings and the above-described preferred embodiments, the present invention is not limited thereto, and is defined by the following claims. Accordingly, those of ordinary skill in the art can variously change and modify the present invention within the scope without departing from the spirit of the claims to be described later.

10: Engine 20: Warm-up catalytic converter (WCC)
30: Fuel Cut Nox Strap (FCNT) 40: Secondary air supply means
50a, 50b, 50c: oxygen sensor 60: three-way catalyst (TWC)
70: hydrocarbon trap (HC TRAP) and three-way catalyst (TWC)

Claims (6)

An exhaust system for a direct injection gasoline turbo engine, comprising:
Direct injection gasoline turbo engine;
secondary air supply means for supplying secondary air to the exhaust gas exhausted from the engine;
a warm-up catalytic converter (WCC) installed downstream from the point at which the secondary air supply means is connected and into which exhaust gas is introduced;
Exhaust of a direct injection gasoline turbo engine including a fuel cut nox strap (FCNT) installed downstream of the warm-up catalytic converter to collect NOx in the fuel cut section and purify NOx by using a reducing agent in the acceleration section system.
The method according to claim 1,
a front-end oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter;
a stopped oxygen sensor for detecting the oxygen concentration of the exhaust gas passing through the warm-up catalytic converter;
The exhaust system of a direct injection gasoline turbo engine further comprising a rear-end oxygen sensor for detecting an oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter.
The method according to claim 1,
a three-way catalyst (TWC) installed downstream of the Fuel Cut Nox Strap to purify harmful substances in the exhaust gas discharged from the Fuel Cut Nox Strap;
a front-end oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter;
The exhaust system of a direct injection gasoline turbo engine further comprising a rear-end oxygen sensor for detecting an oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter.
The method according to claim 1,
a hydrocarbon trap (HC TRAP) installed downstream of the fuel cut nox trap to adsorb hydrocarbons in the exhaust gas discharged from the fuel cut nox trap;
a three-way catalyst (TWC) installed downstream of the Fuel Cut Nox Strap to purify harmful substances in the exhaust gas discharged from the Fuel Cut Nox Strap;
a front-end oxygen sensor for detecting the oxygen concentration of the exhaust gas flowing into the warm-up catalytic converter;
The exhaust system of a direct injection gasoline turbo engine further comprising a rear-end oxygen sensor for detecting an oxygen concentration of the exhaust gas discharged from the warm-up catalytic converter.
A method for controlling an exhaust system of a direct injection gasoline turbo engine, comprising:
a first confirmation step of determining whether the catalyst temperature of the NOx purification means has reached the catalyst activation temperature (LOT) after starting;
a secondary air supply step of increasing the temperature of the exhaust gas by supplying secondary air to the exhaust gas, which is performed when the temperature of the catalyst does not reach the catalyst activation temperature (LOT) in the first checking step;
a second checking step of determining whether the fuel cut section is performed when the temperature of the catalyst reaches the catalyst activation temperature (LOT) in the first checking step;
It is carried out when it is determined that it is not the fuel cut section in the second confirmation step, detects the oxygen concentration of the exhaust gas that is passing or has passed through the warm-up catalytic converter (WCC), and compares the detected value with the lambda value to control rich Or a general control step of performing Lean control;
It is carried out when it is determined that it is the fuel cut section in the second confirmation step, and after applying the fuel cut, the oxygen concentration of the exhaust gas that has passed through the warm-up catalytic converter (WCC) is detected, and the detected value and the lambda value are compared. A control method for an exhaust system of a direct injection gasoline turbo engine, including a fuel cut control step of continuously applying fuel cut if it is in a rich state, and stopping fuel cut if it is in a lean state.
6. The method of claim 5,
In the fuel cut control step, after stopping the fuel cut, NOx contained in the exhaust gas is collected through a fuel cut nox strap (FCNT), the oxygen concentration of the exhaust gas in which the NOx is collected is detected, and the detection value and the lambda value are obtained. In comparison, the method of controlling the exhaust system of a direct injection gasoline turbo engine further comprising the process of applying fuel cut if it is in a rich state, and continuously stopping fuel cut if it is in a lean state.

Images