Patent Publication Number: US-2017350325-A1

Title: Apparatus and method for controlling engine having variable valve actuator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to Korean Patent Application No. 10-2016-0068775 filed in the Korean Intellectual Property Office on Jun. 2, 2016, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an engine and a method for controlling an engine having a variable valve actuator. More particularly, the present disclosure relates to an engine and a method for controlling an engine having a variable valve actuator that operates deactivated cylinders as a pump for recirculating exhaust gas. 
     BACKGROUND 
     Generally, nitrogen oxide (NOx) included in exhaust gas is a cause of acid rain, harms eyes and the respiratory organs, and withers plants. NOx is regulated as a major air pollutant and many researches have been carried out in order to reduce the amount of NOx in the exhaust gas. 
     An exhaust gas recirculation (EGR) system mounted in a vehicle reduces noxious exhaust gases of the vehicle. Generally, the amount of NOx in the exhaust gas is increased in an oxygen rich air mixture, and the air mixture is combusted well. Therefore, the exhaust gas recirculation system reduces the amount of NOx in the exhaust gas as a consequence of a part (e.g., 5-20%) of the exhaust gas being recirculated to the air mixture in order to reduce the oxygen ratio in the air mixture and so hinder combustion. 
     The general EGR system recirculates exhaust gas exhausted from a cylinder of the engine into the cylinder through an EGR line, and an EGR ratio is adjusted by an EGR valve is disposed in the EGR line. 
     The EGR system may be divided into a low pressure EGR (LP EGR) and a high pressure EGR (HP EGR). 
     Conventional EGR system recirculates exhaust gas to the cylinder of the engine through the EGR line, responsiveness is deteriorated when the EGR ratio is controlled by a controller, such as an engine control unit (ECU) of a vehicle. 
     Further, there is a problem that EGR gas cannot be supplied to the cylinder when a back pressure is greater than an intake pressure. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure has been made in an effort to provide an engine and a method for controlling an engine having a variable valve actuator having better responsiveness. 
     Further, the present disclosure has been made in an effort to provide an engine and a method for controlling the engine having a variable valve actuator that can supply EGR gas to the engine when a back pressure is greater than an intake pressure; 
     An apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure includes: the engine including a plurality of cylinders generating a driving torque by burning fuel, an intake valve selectively opened for supplying air and the fuel to the plurality of cylinders through an intake manifold; an exhaust valve selectively opened for exhausting exhaust gas generated from the plurality of cylinders to an exhaust manifold; a variable valve actuator disposed in at least one cylinder among the plurality of cylinders and adjusting a valve characteristic of the intake valve and the exhaust valve; and a controller configured to deactivate the at least one cylinder of the plurality of cylinders through the variable valve actuator according to a driving region of the engine and to recirculate the exhaust gas exhausted from the plurality of cylinders into the intake manifold through the at least one deactivated cylinder; 
     The controller may recirculate exhaust gas to an activated cylinder by opening the exhaust valve of the deactivated cylinder during an intake stroke and opening the intake valve of the deactivated cylinder during an exhaust stroke. 
     The controller may control recirculated exhaust gas amount by adjusting a lift or duration of the exhaust valve and the intake valve through the variable valve actuator; 
     The controller may deactivate the at least one cylinder through the variable valve actuator and recirculate the exhaust gas to the activated cylinder through the at least one deactivated cylinder when the driving region of the engine is a low-speed and a low-load region. 
     A method for controlling an engine having a variable valve actuator according to another exemplary embodiment of the present disclosure includes deactivating, by a controller, at least one cylinder among a plurality of cylinders through a variable valve actuator based on a driving region of the engine; opening, by the controller, an exhaust valve of the at least one deactivated cylinder during an intake stroke; and opening, by the controller, an intake valve of the at least one deactivated cylinder during an exhaust stroke. 
     A recirculated exhaust gas amount may be adjusted by adjusting a lift or duration of the exhaust valve and the intake valve through the variable valve actuator. 
     When the driving region of the engine is a low-speed and a low-load region, at least one cylinder may be deactivated. 
     The intake manifold may integrally include a water to air intercooler. 
     According to the exemplary embodiment of the present disclosure, since EGR gas is directly supplied to an intake manifold, it is possible to improve responsiveness of EGR gas. 
     Further, since EGR gas is compressed by a piston and supplied to the intake manifold, it is possible to supply EGR gas to the engine when back pressure is greater than intake pressure (e.g., low-speed and high-load region). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are referenced merely to describe exemplary embodiments of the present invention, and therefore a technical spirit of the present invention is not to be construed to be limited to the accompanying drawings. 
         FIG. 1  is a schematic view illustrating an apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is a block diagram illustrating an apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
         FIG. 3  to  FIG. 6  are schematic views for explaining operation of an apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
         FIG. 7  is a graph illustrating a driving region of an engine according to an exemplary embodiment of the present disclosure. 
         FIG. 8  is a schematic view illustrating another apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
         FIG. 9  is a flowchart illustrating a method for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present disclosure. 
     Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
     In addition, the size and thickness of each configuration shown in the drawings are arbitrarily shown for better understanding and ease of description, but the present disclosure is not limited thereto. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. 
     Hereinafter, an apparatus for controlling an engine having variable valve actuator according to an exemplary embodiment of the present disclosure will be described in detail with reference to accompanying drawings. 
       FIG. 1  is a schematic view illustrating an apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure.  FIG. 2  is a block diagram illustrating an apparatus for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
     As shown in  FIGS. 1 and 2 , an engine  10  having a variable valve actuator  60  according to an exemplary embodiment of the present disclosure includes a plurality of cylinders  20  in which an intake valve  24  and an exhaust valve  26  are disposed, a variable valve actuator  60  adjusting a lift and a duration of the intake valve  24  and exhaust valve  26 , and a controller  70  operation of the engine  10 , the variable valve actuator  60 , the intake valve, and the exhaust valve  26 . 
     The plurality of cylinders  20  generate driving torque by burning fuel. 
     The intake valve  24  is selectively opened for supplying air and fuel to the cylinder  20 . An operation of the intake valve  24  is controlled by the controller  70 . That is, the intake valve  24  is opened during an intake stroke for supplying air and fuel into the cylinder  20 , and is closed during an exhaust stroke. 
     The exhaust valve  26  is selectively opened for exhausting exhaust gas. An operation of the exhaust valve  26  is controlled by the controller  70 . That is, the exhaust valve  26  is closed during the intake stroke, and is opened during the exhaust stroke for exhausting exhaust gas generated from the cylinder  20 . The variable valve actuator  60  is disposed at some of the cylinders, and selectively deactivates some of the cylinders. When the variable valve actuator  60  is operated, fuel is not supplied to a deactivated cylinder. 
     The opening timing and the closing timing of the intake valve  24  and the exhaust valve  26  are operated by rotation of a crankshaft, and the variable valve actuator  60  advances or retards the opening timing and the closing timing by the controller  70 . And the variable valve actuator  60  adjusts lift of the intake valve  24  and the exhaust valve  26  by the controller  70 . And the variable valve actuator  60  increases or decreases opening time and closing time (hereinafter, refer to ‘duration’) of the intake valve  24  and the exhaust valve  26  by the controller  70 . 
     In an exemplary embodiment of the present disclosure, the variable valve actuator  60  includes a cylinder deactivation apparatus (CDA) deactivating the cylinder  20 , a variable valve lift (VVL) device adjusting lift of the valves, a variable valve timing (VVT) device adjusting the opening timing and the closing timing of the valves, and a variable valve duration (VVD) device adjusting the duration of the valves. 
     The variable valve actuator  60  is widely known in the art, so that a more detailed description thereof will not be presented in the present specification. The controller  70  may be implemented by one or more processors operated by a predetermined program, in which the predetermined program is set to perform steps of the charge method for controlling the engine having the variable valve actuator  60  according to an exemplary embodiment of the present disclosure. 
     The controller  70  deactivates some cylinders  20  of the plurality of cylinders  20  through the variable valve actuator  60  according to a driving region of the engine  10 , and recirculates exhaust gas exhausted from the activated cylinder  20  to an intake manifold  30  through the deactivated cylinder. 
     An operation of the variable valve actuator  60 , an operation of the engine  10 , and the opening and the closing of the intake valve  24  and the exhaust valve  26  are controlled by a control signal of the controller  70 . 
     In detail, the controller  70  deactivates the some cylinders among the plurality of cylinders through the variable valve actuator  60  and recirculates exhaust gas through the deactivated cylinder when the driving region is a low-speed and a low-load region (refer to CDA operation region of  FIG. 7 ). If the cylinder  20  is deactivated, fuel is not injected into the deactivated cylinder. Therefore, it is possible to improve fuel consumption and minimize pumping loss when the some cylinders are deactivated in the low-speed and the low-load region. 
     Referring to  FIG. 3  to  FIG. 6 , a recirculation process of exhaust gas during a deactivation mode that the some cylinders are deactivated will be described in detail. 
       FIG. 3  shows an intake stroke of an activated cylinder in a deactivation mode,  FIG. 4  shows an exhaust stroke of an activated cylinder in a deactivation mode,  FIG. 5  shows an intake stroke of a deactivated cylinder in a deactivation mode, and  FIG. 6  shows an exhaust stroke of a deactivated cylinder in a deactivation mode. 
     As shown in  FIG. 3  and  FIG. 4 , the activated cylinder is normally operated in the deactivation mode. That is, the intake valve  24  is opened during the intake stroke, air flows into the cylinder  20 , and fuel is injected into the activated cylinder by an injector  27 . Fuel injected into the activated cylinder is ignited by a spark plug  28  during a compress stroke. Then, after an explosion stroke, the exhaust valve  26  is opened during an exhaust stroke, and exhaust gas generated at the activated cylinder is exhausted to the exhaust manifold  40 . 
     As shown in  FIG. 5  and  FIG. 6 , air and fuel are not supplied to the deactivated cylinder in the deactivation mode, the exhaust valve  26  is opened and the intake valve  24  is closed through the variable valve actuator  60  controlled by the controller  70 . At this time, exhaust gas exhausted from the activated cylinder flows into the deactivated cylinder  20  through the exhaust manifold  40 . 
     Since air is not supplied to the deactivated cylinder and fuel is not injected into deactivated cylinder, exhaust gas flowing into the deactivated cylinder is compressed during the compress stroke. The intake valve  24  is opened and the exhaust valve  26  is closed through the variable valve actuator  60  controlled by the controller  70  during the exhaust stroke. Since the intake valve  24  is opened during the compress stroke, compressed exhaust gas is exhausted to the intake manifold  30 . 
     Then, the compressed exhaust gas exhausted to the intake manifold  30  is supplied to the activated cylinder  20  during the intake stroke. 
     At this time, the recirculated exhaust gas amount may be adjusted through the lift and the duration of the intake valve  24  and exhaust valve  26 . In the deactivation mode, exhaust gas exhausted from the activated cylinder is resupplied to the activated cylinder through the deactivated cylinder, the deactivated cylinder functions as an exhaust gas recirculation (EGR) apparatus. The deactivated cylinder functions as a kind of a pump when exhaust gas is recirculated through the deactivated cylinder. 
     As such, since exhaust gas exhausted from the activated cylinder is recirculated to the activated cylinder through the deactivated cylinder, it is possible to obtain faster response performance. 
     Further, since exhaust gas is compressed by the piston  29  during exhaust gas recirculation process, it is possible to supply EGR gas to the activated cylinder when back pressure is greater than intake pressure (e.g., low-speed and low-load region). 
     Further, when exhaust gas exhausted from the activated cylinder is recirculated to the activated cylinder through the deactivated cylinder  20  in the deactivation mode, since exhaust gas and engine coolant are heat-exchanged with each other during the compress stroke and the explosion stroke, it is possible to cool EGR gas. 
     Referring to  FIG. 8 , the intake manifold  30  may integrally has a water to air intercooler  32 . Heated coolant at the water to air intercooler  32  is cooled at a radiator  34  passing through a cooling line  36 . As such, if the water to air intercooler  32  integrally includes the intake manifold  30 , cooling performance of the recirculated exhaust gas can be improved when the exhaust gas is recirculated through the deactivated cylinder  20 . 
     Hereinafter, a method for controlling an engine having the variable valve actuator according to an exemplary embodiment of the present disclosure will be described in detail with reference to accompanying drawings. 
       FIG. 9  is a flowchart illustrating a method for controlling an engine having a variable valve actuator according to an exemplary embodiment of the present disclosure. 
     As shown in  FIG. 9 , the controller  70  determines the driving region of the engine  10  at step S 10 . The driving region of the engine  10  may be determined from the required torque of the driver and engine speed. 
     When it is determined that the driving region of the engine  10  is the low-speed and the low-load region, the controller  70  performs the deactivation mode that the some cylinders in the plurality of cylinders are deactivated through the variable valve actuator  60  at step  320 . 
     The controller  70  recirculates exhaust gas exhausted from the activated cylinder to the activated cylinder through the deactivated cylinder at step  320 . The recirculation process of exhaust gas is the same as the above description. 
     When the driving region of the engine  10  is not the low-speed and the low-load region at step the S 10 , the controller  70  activates entire cylinders, and thus, exhaust gas is not recirculated through the deactivated cylinder at step  330 . 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.