Engine system having secondary air injection device

An engine system having a secondary air injection device include: an engine having a plurality of cylinders; a first intake line in which intake air supplied into the cylinder flows; a second intake line in which intake air supplied into the cylinder flows; a bypass line connecting the first intake line and the second intake line; a first electric supercharger and a second electric supercharger disposed in the first intake line and the second intake line, respectively; an exhaust manifold connected with the plurality of cylinders; an exhaust line connected with the exhaust manifold such that exhaust gas flows to the exhaust line through the exhaust manifold; an exhaust gas purification device disposed in the exhaust line; and a secondary air injection device injecting air into the exhaust manifold or the exhaust line from the intake line.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0039069 filed in the Korean Intellectual Property Office on Apr. 4, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a secondary air injection system. More particularly, the present disclosure relates to an engine system having a secondary air injection system that can use an electric supercharger as a pump for secondary air injection.

BACKGROUND

In general, an intake/exhaust system of a vehicle supplies intake air to an engine through an intake manifold, and the intake air supplied to the engine is discharged to outside through an exhaust manifold after combustion in the engine.

In this case, exhaust gas discharged from the engine includes not only harmless materials such as water vapor (H2O), nitrogen (N2), carbon dioxide (CO2), and the like, but also toxic materials such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and the like.

Thus, a secondary air injection system that evokes post combustion by supplying air to the exhaust gas is used in order to remove such toxic materials.

A secondary air injection system according to a conventional art supplies compressed air to an exhaust manifold through a secondary air pump, and then harmful components in the compressed air, supplied to the exhaust manifold, are reduced and then converted to harmless components by a catalytic converter. Through such a process, the exhaust gas is emitted to the outside.

That is, the secondary air pump is used to supply air to an exhaust system at an early operation stage, and the inside of the cylinder is burned richly to reduce harmful components (e.g., unburned hydrocarbons) included in the exhaust gas through the air supplied to the exhaust system.

However, the conventional secondary air injection system requires an additional air pump, thereby causing an increase of the weight, volume, and manufacturing cost of the vehicle.

SUMMARY

The present disclosure has been made in an effort to provide an engine system having a secondary air injection device having a new structure that can reduce the weight, volume, and manufacturing cost of a vehicle by eliminating an additional air pump for secondary air injection.

An engine system having a secondary air injection device according to an exemplary embodiment of the present disclosure may include an engine that includes: a plurality of cylinders that generate a driving torque of a vehicle by combustion of a fuel; a first intake line in which intake air supplied into the cylinder flows; a second intake line in which intake air supplied into the cylinder flows; a bypass line connecting the first intake line and the second intake line; a first electric supercharger and a second electric supercharger disposed on the first intake line and the second intake line, respectively; an exhaust manifold connected with the plurality of cylinders; an exhaust line connected with the exhaust manifold and exhaust gas flows therein; an exhaust gas purification device disposed in the exhaust line; and a secondary air injection device injecting air into the exhaust manifold or the exhaust line from the intake line.

The secondary air injection device may include an air injection line that is branched from the first intake line or the bypass line and then joined to the exhaust manifold or the exhaust line; and an air injection valve that is disposed in the air injection line.

The engine system may further comprise a first intake valve that is disposed in the first intake line; a second intake valve that is disposed in the second intake line; and a bypass valve that is disposed in the bypass line.

The first intake valve may be disposed in a downstream side of the first electric supercharger, and the second intake valve may be disposed in an upstream side of the second electric supercharger.

The air injection line may be branched from the intake line between the first intake valve and the first electric supercharger or the intake line between the bypass valve and the first electric supercharger and then joined to the exhaust manifold or the exhaust line.

The engine system may further include a controller for controlling operations of the engine, the electric supercharger, the first intake valve, the second intake valve, the bypass valve and the air injection valve.

The controller may control the first intake valve and the bypass valve to be closed, the first electric supercharger to be operated such that supercharged air is generated in the first intake line and the bypass line, and adjust an opening of the air injection valve such that the supercharged air is supplied to the exhaust manifold or the exhaust line.

The first intake line and the second intake line are joined to a main intake line, and a main intercooler is disposed in the main intake line.

The engine system may further include a complementary intercooler that is disposed in the bypass line.

According to the exemplary embodiments of the present disclosure, the engine system having the secondary air injection device can perform secondary air injection to an exhaust system by using an electric supercharger, and accordingly, an additional air pump for secondary air injection can be omitted and manufacturing cost of a vehicle can be reduced.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Since the size and the thickness of each configuration shown in drawings are arbitrarily indicated for better understanding and ease of description, the present disclosure is not limited to shown drawings, and the thickness of layers, films, panels, regions, etc., are exaggerated for clarity.

Hereinafter, a secondary air injection device according to a first exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

FIG. 1is a schematic view of an engine system having a secondary air injection device according to an exemplary embodiment of the present disclosure.FIG. 2is a block diagram of an engine system having a secondary air injection device according to an exemplary embodiment of the present disclosure.

As shown inFIG. 1andFIG. 2, an engine system having a secondary air injection device according to an exemplary embodiment of the present disclosure includes an engine10that includes a plurality of cylinders11that generate a driving torque of a vehicle by combustion of a fuel, a plurality of intake lines in which intake air supplied to the cylinders11flows, a first electric supercharger25and a second electric supercharger35that are disposed on the plurality of intake lines, respectively, an exhaust system having an exhaust manifold17and an exhaust line19that is connected with the cylinders11and exhaust gas is discharged, and a secondary air injection device that injects air into the exhaust system (exhaust manifold and/or exhaust line).

An intake valve12is selectively opened/closed to supply air to the cylinder through an intake manifold13. That is, the intake valve12is open during an intake stroke to supply air to the cylinder through the intake manifold13and is closed during an exhaust stroke.

An exhaust valve14is selectively opened/closed to exhaust the exhaust gas generated from the cylinder to the exhaust manifold. That is, the exhaust valve14is closed during the intake stroke, and opened during the exhaust stroke to exhaust the exhaust gas from the cylinder to the exhaust manifold.

Intake air is supplied to the cylinders11of the engine10passing through the plurality of intake lines, and exhaust gas discharged from the cylinders11is exhausted to the outside through the exhaust manifold17and the exhaust line19. In this case, an exhaust gas purification device70is disposed on the exhaust line19. The exhaust gas purification device70may be a catalytic converter or a diesel particulate filter (DPF) in case of a diesel engine.

The plurality of intake lines includes a first intake line20and a second intake line30which external air supplied to the cylinders11flows. However, this is not restrictive.

A bypass line40which connects the first intake line20and the second intake line30is disposed between the first intake line20and the second intake line30. That is, the bypass line40is branched from the first intake line20and merged into the second intake line30.

The first and second electric superchargers25and35disposed in the first intake line20and the second intake line30, respectively, are for supplying compressed air to the cylinders. The first electric supercharger includes a motor21and an electric compressor23, and the second electric supercharger includes a motor31and an electric compressor33. The electric compressors23and33are operated by the motors21and31, respectively, and compress intake air, and the compressed intake air is supplied to the cylinders11.

A first intake valve27is disposed in the first intake line20. The first intake valve27may be disposed in a downstream portion of the first electric supercharger25disposed in the first intake line20. Intake air amount supplied through the first intake line20is adjusted by opening of the first intake valve27.

A second intake valve37is disposed in the second intake line30. The second intake valve37may be disposed in a downstream portion of the second electric supercharger35disposed in the second intake line30. Intake air amount supplied through the second intake line30is adjusted by opening of the second intake valve37.

The first intake line20and the second intake line30are merged into a main intake line50, and a main intercooler54is disposed in the main intake line50. Supercharged air compressed by the electric supercharger is cooled by the main intercooler54.

A bypass valve47is disposed in the bypass line40. A complementary intercooler43may be disposed in the bypass line40. Supercharge air compressed by the first electric supercharger25is cooled by the complementary intercooler43.

An air cleaner52for filtering external air is disposed in an entrance of the first intake line20and the second intake line30.

External air inflowing through the first intake line20and the second intake line30is supplied to the cylinders11through an intake manifold13. A throttle valve15is disposed in the intake manifold13, and adjusts air amount supplied to the cylinder11.

The secondary air injection device injects air into an exhaust system (exhaust manifold and/or exhaust line) from the intake line, and includes an air injection line100and an air injection valve110disposed in the air injection line100.

The air injection line100is branched from the first intake line20or the bypass line40and joined to the exhaust manifold17or the exhaust line19. The air injection valve110is disposed in the air injection line100and air amount supplied to the exhaust system by opening of the air injection valve110.

The engine system according to an exemplary embodiment of the present disclosure may further include a cylinder deactivation (CDA) system60selectively deactivating some of the plurality of cylinders11.

The CDA system60may control some of the cylinders, and selectively deactivates some of the cylinders. When the CDA system60is operated, fuel is not supplied to a deactivated cylinder, and operation of an intake valve12and an exhaust valve14is stopped.

The CDA system60is widely known in the art, and therefore, detailed description thereof is omitted herein.

The CDA system60may control a second cylinder and a third cylinder among four cylinders.

The engine system according to an exemplary embodiment of the present disclosure may further include a driving information sensor80detecting driving information of a vehicle, and a controller90controlling operations of the first intake valve27, the second intake valve37, the bypass valve47, the first electric supercharger25, the second electric supercharger35, the CDA system60, the throttle valve15and the air injection valve110based on the driving information.

The driving information sensor80detects the driving information including an engine torque, an engine speed, and a required torque of a driver. The driving information is then transmitted to the controller90.

The controller90may be provided as at least one processor operating by a predetermined program, and the predetermined program performs each step of a method for controlling the engine system according to an exemplary embodiment of the present disclosure. The controller90may be an electronic control unit (ECU).

Hereinafter, operations of the engine system having the secondary air injection device according to an exemplary embodiment of the present disclosure will be described in detail with reference to accompanying drawings.

The controller90determines a driving region of the engine based on the driving information detected by the driving information sensor80. The driving region may be divided into a low speed and low load region, a low and middle speed and high load region, and a high speed and high load region.

The controller90adjusts supercharged air amount supplied to the cylinders11through controlling the first intake valve27, the second intake valve37and the bypass valve47based on the driving region of the engine. That is, the controller90controls opening and closing of the first intake valve27, the second intake valve37and the bypass valve47, or opening degree of the first intake valve27, the second intake valve37and the bypass valve47, such that supercharged air amount supplied to the cylinders11is adjusted.

In addition, the CDA system60may be embedded in or connected to the controller90such that the controller90can control deactivation of cylinders.

Referring toFIG. 3, in the low and middle speed and high load region, the controller90controls that the first intake valve27and the second intake valve37are closed and controls opening degree of the bypass valve47, such that supercharged air amount supplied to the cylinder11is adjusted. Further, the controller90operates the first electric supercharger25and the second electric supercharger35, such that supercharged air by the first electric supercharger25and the second electric supercharger35is supplied to the cylinder11.

That is, external air inflowing through the first intake line20is primarily compressed by the electric supercharger25, and the external air flows into the second intake line30passing through the bypass line40. Then, the external air is additionally compressed by the second electric supercharger35.

Since high compression ratio is needed in the low and middle speed and high load region, it is possible to increase the compression ratio of external air supplied to the cylinder11by operating the first electric supercharger25and the second electric supercharger35in series. Further, since external air compressed by the electric supercharger25is cooled by the complementary intercooler43, compression efficiency of external air can be improved.

Referring toFIG. 4, in the high speed and high load region, the controller90controls that the bypass valve47is closed and controls opening degree of the first intake valve27and the second intake valve37, such that supercharged air amount supplied to the cylinders11is adjusted. Further, the controller90operates the first electric supercharger25and the second electric supercharger35, such that supercharged air by the first electric supercharger25and the second electric supercharger35is supplied to the cylinders11.

Since a lot of external air supplied to the cylinders is necessary in the high speed and high load region, external air is supplied to the cylinders through the first intake line20and the second intake line30. In this case, a lot of external air can be supplied to the cylinders11by operating the first electric supercharger25and the second electric supercharger35in parallel.

Referring toFIG. 5, in the low speed and low load region, the controller90deactivates some of the cylinders11by operating the CDA system60. The controller90controls that the first intake valve27and the second intake valve37are closed and controls opening degree of the bypass valve47, such that supercharged air amount supplied to the cylinders11is adjusted. Then, the controller90operates the first electric supercharger25and the second electric supercharger35, such that that supercharged air by the first electric supercharger25and the second electric supercharger35is supplied to the cylinders11.

That is, external air inflowing through the first intake line is primarily compressed by the electric supercharger25, and the external air flows into the second intake line30passing through the bypass line40. Then, the external air is additionally compressed by the second electric supercharger35.

Since some cylinders are deactivated in the low speed and low load region (the driving region in which the CDA system operates), unnecessary pumping loss is reduced and fuel consumption can be improved. Further, since supercharged air is supplied to the cylinder11by using two electric superchargers in the low speed and low load region, the driving region in which the CDA system operates can be expanded.

Referring toFIG. 6, when air needs to be supplied to the exhaust system (exhaust manifold and/or exhaust line), the controller90controls that the first intake valve27and the bypass valve47are closed, and operates the first electric supercharger25such that supercharged air is generated in the first intake line20between the first electric supercharger25and the first intake valve27or the bypass line40between the first electric supercharger25and the bypass valve47. When the controller90controls that the air injection valve110is opened, air is supplied to the exhaust system from the first intake line20and/or the bypass line30by supercharged pressure. At this time, when an opening degree of the air injection valve110is adjusted, air amount supplied to the exhaust system is adjusted.

Then, exhaust gas is post-combusted by the secondary air supplied to the exhaust system such that harmful components included in the exhaust gas are removed. In addition, intake air is supplied to the cylinder of the engine10through the second line30.

At this time, intake air is compressed by the second electric supercharger35and supplied passing through the second intake line30.

In the engine system having the secondary air injection device according to the above-described exemplary embodiments of the present disclosure, the second electric supercharger35performs a function as a conventional air pump for secondary air injection, and thus no additional air pump for secondary air injection is required.