System and method for controlling a vehicle during cold start

Abstract

A method for controlling a hybrid vehicle for a cold start is presented. The method includes determining whether an internal combustion engine of the vehicle is idling. If the engine is idling, the method further includes increasing a load of a hybrid starter / generator (HSG) until a selective catalytic reduction (SCR) catalyst reaches a desired temperature.

Description

BACKGROUND OF THE INVENTION(a) FIELD OF THE INVENTION

[0001] The present disclosure relates to a vehicle control system and method for cold starting. (b) DESCRIPTION OF RELATED FACTS

[0002] A typical vehicle is powered using energy generated by the combustion of an air-fuel mixture. Recently, the use of hybrid vehicles has increased to respond to increased emissions regulations and improve fuel efficiency.

[0003] A hybrid vehicle is a vehicle that uses two or more energy sources. Generally, a hybrid vehicle includes an internal combustion engine powered by the combustion of fossil fuel and a motor powered by electrical energy stored in a battery as energy sources.

[0004] Since a 48V battery is applied to the vehicle, interest in mild hybrid vehicles is increasing. The mild hybrid vehicle uses the engine as a primary power source and uses the motor to assist the engine. In other words, the motor of the mild hybrid vehicle is usually connected to the engine to start the engine, assists with torque while driving the engine, and charges the battery using the remaining energy when the engine is driving. In addition, the exhaust gas produced by the combustion process contains various materials (e.g., hydrocarbons, carbon dioxide, or nitrogen oxide), and some of the various materials contained in the exhaust gas must be removed to comply with environmental regulations.

[0005] The document DE 10 2007 010 197 A1 relates to a method for heating a catalyst in a hybrid vehicle, as well as to a hybrid vehicle.

[0006] The document DE 10 2016 115 135 A1 relates to internal combustion engines and in particular to a method for reducing NOx emissions from a motor vehicle engine during acceleration of the vehicle.

[0007] The above information disclosed in this Background section is provided merely to facilitate understanding of the background of the invention. Applicant cautions that this section may contain information that predates this application. SUMMARY

[0008] The invention provides a vehicle control system according to claim 1 and a vehicle control method according to claim 5. Preferred embodiments are subject of the subclaims.

[0009] Generally, the exhaust gas discharged through an engine's exhaust manifold is directed to a catalytic converter installed in an exhaust pipe for purification, passes through a muffler to reduce noise, and is then discharged to the atmosphere through a tailpipe. The catalytic converter purifies impurities contained in the exhaust gas. Furthermore, a soot filter for collecting particulate matter (PM) contained in the exhaust gas is attached to the exhaust pipe.

[0010] A denitrification catalyst (DeNOx catalyst) is a catalytic converter that purifies nitrogen dioxide (NOx) contained in exhaust gases. When a reducing agent, such as urea, ammonia, carbon monoxide, and hydrocarbons (HC), is introduced into the exhaust gas, the nitrogen oxide contained in the exhaust gas is reduced through an oxidation-reduction reaction process with the reducing agent in the denitrification catalyst.

[0011] A selective catalytic reduction (SCR) catalyst is a denitrification catalyst. Recently, the use of SCR catalysts has increased due to tightening exhaust regulations. SCR catalysts work well within a specified temperature range (approximately 250°C to 400°C). However, there is a problem in that the SCR catalyst cannot remove nitrogen oxide at low temperatures and excessively decomposes nitrogen oxide at high temperatures, resulting in the release of ammonia.

[0012] Since most of the nitrogen oxide emitted by the vehicle is released at the beginning of an engine start, rapid warm-up of the engine is particularly important to reduce emissions.

[0013] The present disclosure was made with the intention of providing a vehicle control system and method at cold start that increases a load of an HSG when an engine is in an idling state and a temperature of an SCR catalyst is low at cold start, to shorten a warm-up time of an engine and to assist engine torque by using an HSG when the engine is not driven in an idling state and nitrogen oxides need to be purified to improve fuel efficiency.

[0014] The difference between the temperature of the SCR catalyst and the predetermined temperature may be divided into two or more temperature difference ranges, and the predetermined load amount in any temperature difference range may be constant.

[0015] As the engine is running at the time of cold start, the controller may determine whether an amount of nitrogen oxide contained in the exhaust gas is greater than a reference amount, and if the amount of nitrogen oxide contained in the exhaust gas is greater than the reference amount, the controller may control the injection module to inject a reducing agent in accordance with the amount of nitrogen oxide.

[0016] The controller may control the HSG to produce at least a portion of a driver's requested torque prior to injection of the reducing agent.

[0017] If the temperature of the SCR catalyst is higher than the second temperature, the method may further comprise: returning to the determination of an engine state.

[0018] The method may further comprise: additionally injecting the fuel when the engine is in a rest or idle state.

[0019] When the engine is not in an idling state, the method may further include: determining whether an amount of nitrogen oxide contained in the exhaust gas is greater than a reference amount; calculating a reducing agent injection amount according to the amount of nitrogen oxide when the amount of nitrogen oxide contained in the exhaust gas is greater than the reference amount (the reference amount); and injecting the reducing agent according to the calculated reducing agent injection amount.

[0020] If an amount of nitrogen oxide contained in the exhaust gas is greater than the reference amount(s), then the method may further comprise: generating at least a certain amount of a driver's requested torque by the HSG before injecting a reducing agent.

[0021] According to the embodiment of the present invention, when the engine is in an idle state and a temperature of the SCR catalyst at cold start is low, a load of the HSG is increased to shorten a warm-up time of the engine.

[0022] When the engine is not in an idle or resting state and nitrogen oxides need to be cleaned, the engine torque would be assisted using the HSG to improve fuel efficiency.

[0023] In addition, effects that can be obtained or predicted by the embodiment of the present invention are directly or implicitly disclosed in the detailed description of the embodiment of the present invention. That is, various effects that can be predicted according to the embodiment of the present invention are disclosed in the detailed description that will be described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings show: Fig. 1 is a schematic diagram of a vehicle control system according to an embodiment of the present invention; Fig. 2 is a block diagram illustrating a relationship between an input and an output of a controller used for a vehicle control method in accordance with an embodiment of the present invention; and Fig. 3 is a flowchart of a vehicle control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be described in more detail below with reference to the accompanying drawings, in which embodiments of the invention are shown. As those of ordinary skill in the art will appreciate, the described embodiments may be modified in various different ways, all of which, however, do not depart from the scope and spirit of the present invention.

[0026] The drawings and description are to be considered as illustrative in nature and not restrictive, and like reference characters designate similar elements throughout the description.

[0027] In the following description, a division of names of components into the first, the second, and the like is provided to divide the names because the names of the components are the same to each other and an order thereof is not particularly limited.

[0028] Terms used in the description are used to describe specific embodiments only, but are not intended to limit the present invention. As used in the description, singular forms are intended to include plural forms unless explicitly described to the contrary. The terms "includes" and / or "including" used in the description specify the presence of features, numbers, steps, operations, individual elements, and / or components, but should be understood not to exclude one or more other features, numbers, steps, operations, and / or groups thereof. As used in the description, a term "and / or" includes any or all combinations of one or more related specified parts.A term “coupled” represents a physical relationship between two components and the components are directly connected to each other or indirectly connected to each other via at least one intermediate component.

[0029] As used in the specification, it should be noted that the term "vehicle," "vehicular," or other similar terms includes automobiles in general, passenger vehicles, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including various boats and ships, and aircraft, and also includes a hybrid vehicle, an electric vehicle, a hybrid electric vehicle, a hydrogen-powered vehicle, and other alternative fuel vehicles (fuels derived from resources other than oil). As mentioned earlier in the specification, an electric vehicle (IV) is a form of transportation and is a vehicle with electrical energy obtained from a rechargeable energy storage device (e.g., one or more rechargeable electrochemical cells or another type of battery).The term "e-vehicle" is not limited to a single vehicle, but includes motorcycles, carts, and scooters. Furthermore, a hybrid vehicle is a vehicle with two or more power sources, such as gasoline-assisted power and electric-assisted power (e.g., a hybrid electric vehicle (HEV)).

[0030] Additionally, one or more of the following methods or aspects may be performed by at least one controller, a control unit network (CAN) bus, or a vehicle network. The controller, the control unit network (CAN) bus, or the vehicle network may be implemented in the vehicle described in the specification. A term "controller" may refer to a hardware device having a memory and a processor. Memory is configured to store program instructions, and the processor is specifically programmed to execute program instructions that perform at least one process described below. The following methods, as described in greater detail below, may be further performed by a system including the controller by connecting them to at least one additional component.

[0031] Furthermore, the method of the present description may be implemented as a non-transitory computer-readable storage medium on a computer-readable storage medium containing executable program instructions executed by a processor or a controller. Examples of the computer-readable storage medium include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable storage media may be distributed in a network connected to computer systems for storage and execution, such as being distributed by a telematics server or a control unit network (CAN).

[0032] One aspect of the present invention provides a method for controlling a motor / generator (HSG, 70) after a cold start of a hybrid vehicle. After a cold start of the vehicle, at least one controller of the vehicle determines (1) whether or not an internal combustion engine 10 is in an idle state, and (2) whether a temperature of an SCR catalyst unit 60 is lower than a first predetermined temperature (a lower limit of a desirable operating range of the SCR catalyst unit 60).

[0033] Thereafter, when the engine 10 is cold (at a temperature lower than a predetermined temperature) and at idle or rest, and when the temperature of the SCR catalyst unit 60 is lower than the first predetermined temperature, the vehicle's controller thereafter causes the motor / generator 70 to run at a first load level that is higher than a normal load level (by activating a clutch to couple or press the HSG 70 and the engine 10 together, and / or by placing a negative torque command to the HSG 70). In embodiments, the HSG 70 operates at a normal load level when the engine is idle or resting and the temperature of the SCR catalyst unit is within the desired operating range.

[0034] Thereafter, when the temperature of the SCR catalyst unit 60 reaches the desired range and the engine is still idling, the controller causes the motor / generator 70 to operate at a second load level lower than the first load level. In embodiments, when the engine stops idling in response to the driver's application of an accelerator pedal (and begins to propel the vehicle), the controller (1) causes the motor / generator 70 to operate at a third load level (to generate additional torque in addition to the torque from the engine) even when the SCR catalyst unit 60 reaches its desired operating range, and (2) controls the injector 40 to spray a reductant into the exhaust gas when the NOx level is higher than a predetermined reference. In embodiments, the third load level is lower than the first load level.

[0035] In embodiments, when the engine 10 is cold (at a temperature lower than a predetermined temperature) and idling (or resting), the injector 40 does not operate to spray a reductant into the exhaust gas, regardless of the NOx level, while the motor / generator 70 operates at the first load level for rapid warm-up of the SCR catalyst unit 60. In other words, the injector 40 injects the reductant into the exhaust gas while the engine is idling if the temperature of the SCR catalyst has not reached the desired operating range after a cold start.

[0036] Fig. 1 is a schematic diagram of a vehicle control system according to an embodiment of the present invention.

[0037] How Fig. 1, a vehicle control system according to an embodiment of the present invention includes an engine 10, an exhaust pipe 20, a soot filter 30, an injection module 40, a selective catalytic reduction (SCR) catalyst 60, a hybrid starter / generator (HSG), a battery 72, and a controller 80.

[0038] Here, the HSG is exemplified as a mild hybrid starter / generator (MHSG). However, the HSG is not limited to the MHSG, and a conventional HSG is sufficient if the HSG performs a function of an HSG according to an embodiment of the present invention.

[0039] The engine 10 converts chemical energy into mechanical energy by combusting an air-fuel mixture. The engine 10 is connected to an intake manifold 16 to introduce air into a combustion chamber 12, and the exhaust gas generated during a combustion process is collected in an exhaust manifold 18 and then discharged from the engine 10 to the outside. An injector 14 is mounted in the combustion chamber 12 to inject fuel into the combustion chamber 12.

[0040] A diesel engine is exemplified here, but a lean-burn gasoline engine can also be used. When a gasoline engine is used, the air-fuel mixture flows into the combustion chamber 12 via the intake manifold 16, and a spark plug is mounted above the combustion chamber 12 for ignition. When a gasoline direct injection (GDI) engine is used, the injector 14 is mounted above the combustion chamber 12, similar to the diesel engine.

[0041] The mechanical energy generated in the engine 10 is transmitted to the wheels 100 via a transmission to drive the vehicle.

[0042] The exhaust pipe 20 is connected to the exhaust manifold 18 to discharge the exhaust gas from the vehicle to the outside. The particulate filter 30, the injection module 40, and the SCR catalyst 60 are mounted on the exhaust pipe 20 to remove hydrocarbons, carbon monoxide, particulate matter, and nitrogen oxide contained in the exhaust gas.

[0043] The soot filter 30 is mounted on the exhaust pipe 20 at a rear end of the engine 10 and collects particulate matter. Typically, the soot filter 30 includes a plurality of intake ports and exhaust ports. One end of the intake port is open, and the other end is closed, so that exhaust gas from the front end of the soot filter 30 flows therein. Further, one end of the exhaust port is closed, and the other end is open, so that exhaust gas is discharged into the soot filter 30. The exhaust gas flowing into the soot filter 30 via the intake port enters the exhaust port via a porous wall dividing the intake port and the exhaust port, and is then discharged from the soot filter 30 via the exhaust port. The particulate matter (i.e., soot) contained in the exhaust gas is collected as the exhaust gas flows through the porous wall.

[0044] Additionally, a differential pressure sensor 32 is mounted in the exhaust pipe 20. The differential pressure sensor 32 measures a pressure difference between a front end and a rear end of the soot filter 60 and transmits a signal corresponding thereto to the controller 80. When a differential pressure measured by the differential pressure sensor 32 is equal to or higher than a predetermined pressure, the controller 80 controls the soot filter 30 to be regenerated. In this case, the injector 14 performs post-injection of fuel to burn the particulate matter collected in the soot filter 30. When a temperature of the exhaust gas flowing through the soot filter 30 is low, the controller 80 increases a load of the MHSG 70 to heat the exhaust gas.

[0045] A first temperature sensor 82 is mounted in the exhaust pipe 20 on the front side of the soot filter 30 to detect a temperature of an exhaust gas flowing to the soot filter 30. Further, a second temperature sensor 84 is mounted on a rear exhaust pipe 20 of the soot filter 30 to detect a temperature of the exhaust gas discharged from the soot filter 30.

[0046] Here, it is exemplified that the first and second temperature sensors 82 and 84 are arranged on a front and a rear side of the soot filter. However, the embodiment of the present invention is not limited to the use of both the first and second temperature sensors 82 and 84, but any of the first and second temperature sensors 82 and 84 may be used. Furthermore, a temperature of the soot filter 30 may mean a temperature of the exhaust gas flowing through the soot filter 30 and may be determined based on any one of the measured values ​​of the first temperature sensor 82, a measured value of the second temperature sensor 84, and measured values ​​of the first and second temperature sensors 82 and 84.

[0047] The injection module 40 is mounted in the exhaust pipe 20 at a rear end of the soot filter 30 and is controlled by the controller 80 to inject a reducing agent into the exhaust gas. Typically, the injection module 40 injects urea, and the injected urea is converted into ammonia through hydrolysis. However, the reducing agent is not limited to ammonia.

[0048] A mixer 50 is mounted on the exhaust pipe 20 at a rear end of the injection module 40 to uniformly mix the reducing agent with the exhaust gas.

[0049] The SCR catalyst 60 is mounted in the exhaust pipe 20 at a rear end of the soot filter 30 and reduces nitrogen oxide contained in the exhaust gas using the reducing agent injected from the injection module 40.

[0050] A NOx sensor 86 is mounted in the exhaust pipe 20 on the front side of the SCR catalyst 60. The first NOx sensor 86 measures an amount of nitrogen oxide contained in the exhaust gas flowing to the SCR catalyst 60 to send a corresponding signal to the controller 80. The amount of NOx measured by the first NOx sensor 86 is used to determine an amount of reductant to be injected by the injection module 40.

[0051] The third temperature sensor 88 detects a temperature of the exhaust gas discharged from the SCR catalyst 60. Here, it is exemplified that the second and third temperature sensors 84 and 88 are arranged on the front and rear sides of the SCR catalyst 60. However, the embodiment of the present invention is not limited to the use of both the second and third temperature sensors 84 and 88, but only one of the second and third temperature sensors 84 and 88 may be used. Further, a temperature of the SCR catalyst 60 may mean a temperature of the exhaust gas flowing through the SCR catalyst 60, and may be determined based on any one of the measured values ​​of the second temperature sensor 84, a measured value of the third temperature sensor 88, and measured values ​​of the second and third temperature sensors 84 and 88.

[0052] The NOx sensor 90 detects an amount of nitrogen oxide contained in the exhaust gas discharged from the SCR catalyst 60 and transmits a signal corresponding thereto to the controller 80. The controller 80 may monitor whether the SCR catalyst 60 removes nitrogen oxide contained in the exhaust gas based on a detected value of the second NOx sensor 90. That is, the second NOx sensor 90 may be used to evaluate an operating behavior of the SCR catalyst 60.

[0053] The MHSG 70 is mounted on one side of the engine 10 and is selectively or continuously connected to a crankshaft of the engine 10. The MHSG 70 rotates the crankshaft using electrical energy from the battery 72 to start the engine 10 and to assist torque while driving the engine 10. Furthermore, the MHSG 70 generates electricity using the energy generated in the engine 10 and charges the battery 72 with the generated electricity.

[0054] Battery 72 supplies electricity to electrical components of the vehicle. Specifically, battery 72 supplies electrical energy to MHSG 70 to start engine 10 or assist the torque of engine 10. Furthermore, battery 72 may be charged by the electrical energy generated in MHSG 70. Battery 72 may include, but is not limited to, a 48V battery.

[0055] The controller 80 determines a driving condition of the engine 10 based on signals detected by sensors, and controls operations of the engine 10 and the MHSG 70 based on the driving condition of the engine 10. Further, the controller 80 calculates an amount of soot collected by the soot filter 30 and controls the soot filter 30 to be regenerated when the amount of soot is equal to or greater than a predetermined amount. When regeneration of the soot filter 30 starts when the temperature of the soot filter 30 is low, the controller 80 controls the MHSG 70 to heat the soot filter 30. Further, the controller 80 reports an amount of nitrogen oxide contained in the exhaust gas.When the nitrogen oxide amount is greater than a reference amount, the controller 80 controls an amount of a reducing agent that is injected and controls the injection module 40 to inject the reducing agent according to the amount of the injected reducing agent.

[0056] Furthermore, a plurality of maps and a plurality of models defining characteristics of the SCR catalyst 60 are stored in the controller 80. The controller 80 calculates an amount of ammonia adsorbed in the SCR catalyst 60 based on the maps and the models, and adjusts the amount of reducing agent to be added according to an amount of ammonia absorbed by the SCR catalyst 60. The plurality of maps and the plurality of models can be determined through a large number of experiments.

[0057] In this regard, the controller 80 may be implemented by at least one processor operated by a predetermined program, and the predetermined program may be programmed to execute each step of the vehicle control method according to the embodiment of the present invention.

[0058] Fig. 2 is a block diagram illustrating a relationship between an input and an output of a controller used for a vehicle control method according to an embodiment of the present invention.

[0059] How Fig. 2, the first temperature sensor 82, the second temperature sensor 84, the first NOx sensor 86, the third temperature sensor 88, the second NOx sensor 90 and the differential pressure sensor 82 are electrically connected to the controller 80 and transmit sensed values ​​to the controller 80.

[0060] The first temperature sensor 82 detects a temperature of the exhaust gas flowing to the soot filter in order to send a signal corresponding thereto to the controller 80.

[0061] The second temperature sensor 84 measures a temperature of the exhaust gas emitted from the soot filter 30 to send a corresponding signal to the controller 80.

[0062] The first NOx sensor 86 measures an amount of NOx contained in the exhaust gas flowing to the SCR catalyst 60 to send a signal corresponding thereto to the controller 80.

[0063] The third temperature sensor 88 measures a temperature of the exhaust gas discharged from the SCR catalyst 60 to send a signal corresponding thereto to the controller 80.

[0064] The second NOx sensor 90 detects an amount of nitrogen oxide contained in the exhaust gas discharged from the SCR catalyst and transmits a signal corresponding thereto to the controller 80.

[0065] The differential pressure sensor 32 measures a pressure difference between a front end and a rear end of the soot filter 30 and transmits a signal corresponding thereto to the controller 80.

[0066] The controller 80 determines an engine driving condition, a fuel injection amount, a fuel injection timing, a fuel injection pattern, a reducing agent injection amount, a regeneration timing of the soot filter 30, and a charging amount of the MHSG 70 based on the sent values, and outputs signals for controlling the injector 14, the injection module 40, and the MHSG 70 to the injector 14, the injection module 40, and the MHSG generator 70. Further, the controller 80 calculates an amount of ammonia adsorbed on the SCR catalyst 60 based on the sent values, and calculates an amount of the reducing agent to be injected from the injection module 40 based on the ammonia amount.

[0067] Meanwhile, a plurality of sensors in the vehicle control system according to the embodiment of the present invention, including sensors other than those described with reference to Fig. 2, but a description of them is omitted for the sake of clarity of the description.

[0068] Furthermore, the positions of the sensors can vary depending on the requirements and the positions shown in Fig. 1 shown positions.

[0069] Fig. 3 is a flowchart of a vehicle control method according to an embodiment of the present invention. As in Fig. As shown in Figure 3, a vehicle control method according to an embodiment of the present invention starts by determining whether a cold start condition of an engine 10 is satisfied in step S305. That is, the controller 80 determines whether torque of the engine 10 is required in a state where the engine 10 is not warmed up. For example, the cold start condition is satisfied when starting the engine 10 is required and a temperature of a coolant is lower than a predetermined temperature. In embodiments, the engine is cold when the temperature of the engine coolant is lower than a predetermined temperature or the temperature of the engine is lower than a predetermined temperature.

[0070] In step S305, the controller 80 continuously determines whether the cold start condition is met. If the cold start condition is met in step S305, the controller 80 starts the engine 10 and determines a state of the engine 10 in step S310. That is, the controller 80 determines whether the engine 10 is in an idle state or the engine 10 is operating in a non-idle state (driving the vehicle).

[0071] When the engine 10 is operating in an idling state in step S310, the controller 80 controls the injector 14 to additionally inject the fuel in step S315. That is, the controller 80 controls the injector 14 to inject more fuel in addition to the fuel for adjusting a required torque of the engine 10 according to a predetermined map.

[0072] Further, the controller 80 checks a temperature of the SCR catalyst 60. That is, the controller 80 checks a difference between the temperature of the SCR catalyst 60 and a predetermined temperature to determine whether the temperature of the SCR catalyst 60 is sufficient to effectively remove nitrogen oxide. In the embodiment of the present invention, the difference between the temperature of the SCR catalyst 60 and the predetermined temperature is divided into three temperature difference sections, and the controller 80 controls the engine 10 and the HSG 70 according to the same control strategy in each temperature difference section. However, the number of temperature difference sections is not limited to three. Further, the controller 80 may continuously control the engine 10 and the HSG 70 according to the difference between the temperature of the SCR catalyst 60 and the predetermined temperature.

[0073] How Fig.3, the controller 80 determines whether the temperature of the SCR catalyst 60 is included in a first temperature difference range. In other words, the controller 80 determines whether the temperature of the SCR catalyst 60 is lower than a first temperature in step S320. If the temperature of the SCR catalyst 60 is lower than the first temperature in step S320, the controller 80 increases the load of the HSG 70 by a first load in step S325. Normally, the controller 80 controls the injector 14 to inject fuel according to a predetermined map to meet a torque requested by the driver. However, if the load of the HSG 70 is increased, the load of the HSG 70 acts as a friction force. Therefore, the controller 80 controls the injector 14 to inject more fuel to meet the torque requested by the driver. Therefore, the temperature of the exhaust gas rises sharply.In addition, as a method for increasing the load of the HSG 70, a clutch that selectively connects the crankshaft of the engine 10 and a shaft of the HSG 70 is actuated (to couple the crankshaft and the shaft of the HSG), or a negative torque command is given to the HSG 70. However, the method for increasing the load of the HSG 70 is not limited to those exemplified and may use a suitable method among various methods known to one of ordinary skill in the art.

[0074] After executing step S325, the controller 80 returned to step S315.

[0075] In step S320, when the temperature of the SCR catalyst 60 is equal to or higher than the first temperature, the controller 80 determines whether the temperature of the soot filter 30 is included in the second temperature difference section or the third temperature difference section. In other words, the controller 80 determines whether the temperature of the SCR catalyst 60 is higher than the second temperature in step S330. If the temperature of the SCR catalyst 60 is equal to or lower than the second temperature in step S330, the controller 80 increases the load of the HSG 70 by a second load in step S340. The second load is smaller than the first load. Next, the controller 80 returns to step S315.

[0076] If the temperature of the SCR catalyst 60 is higher than the second temperature in step S330, then the controller 80 returned to step S310 to determine the state of the engine.

[0077] If the engine 10 is not in an idling state in step S310, then the controller 80 changes a load of the HSG 70 to an initial value (for example, 0) and determines whether the amount of nitrogen oxide contained in the exhaust gas is greater than a reference amount in step S345.

[0078] When the amount of nitrogen oxide contained in the exhaust gas is equal to or less than the reference amount in step S345, the controller 80 ends the vehicle control process according to the present embodiment.

[0079] If the amount of nitrogen oxide contained in the exhaust gas is greater than the reference amount in step S345, the controller assists the torque of the engine 10 using the HSG 70 in step S3150. In other words, the controller 80 causes the HSG 70 to generate a portion of a target torque and reduce the torque of the engine 10. Therefore, since the fuel injection amount is reduced, fuel efficiency is improved.

[0080] Further, the controller 80 calculates a reducing agent injection amount to be injected from the injection module 40. The reducing agent injection amount can be calculated according to an amount of ammonia adsorbed on the SCR catalyst 60, an amount of nitrogen oxide contained in the exhaust gas, the temperature of the SCR catalyst 60, and a deterioration factor of the SCR catalyst 60. A method for calculating the reducing agent injection amount is well known to one of ordinary skill in the art, so a detailed description thereof will be omitted.

[0081] Next, the controller 80 controls the injection module 40 to inject the reducing agent according to the reducing agent injection amount in step S360. When the reducing agent is injected into the exhaust gas so that nitrogen oxide contained in the exhaust gas is removed in the SCR catalyst 60, the controller 80 returns to step S345.

[0082] Logical blocks, modules, or units described in connection with the embodiments discussed herein may be implemented by or executed by a computing device having at least one processor, at least one memory, and at least one communication interface. The elements of a method, process, or algorithm described in connection with disclosed embodiments may be implemented directly in hardware, in a software module executed by at least one processor, or in a combination of the two. Computer-readable instructions for implementing a method, process, or algorithm described in connection with disclosed embodiments may be stored in a non-transitory computer-readable storage medium.

[0083] While this invention has been described in connection with embodiments, it should be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements that fall within the spirit and scope of the appended claims.

Claims

[1] Vehicle control system comprising: an engine (10) having a combustion chamber (12) configured to generate energy by combustion of an air-fuel mixture, an intake manifold (16) configured to supply air to the combustion chamber (12), an injector (14) configured to supply fuel to the combustion chamber (12), and an exhaust manifold (18) configured to discharge exhaust gas generated by combustion of the air-fuel mixture to an exhaust pipe (20); a hybrid starter / generator (HSG) (70) configured to start the engine (10) or generate electricity using energy generated in the engine (10); an injection module (40) mounted in the exhaust gas and injecting a reducing agent into the exhaust gas; a selective catalytic reduction (SCR) catalyst (60) mounted in the exhaust pipe (20) at a rear end of the injection module (40) and reducing nitrogen oxide contained in the exhaust gas using the reducing agent; and a controller (80) which controls operations of the injector (14), the injection module (40), and the HSG (70), wherein, when a state of the engine (10) is an idle state at the time of a cold start, the controller (80) increases a load of the HSG (70) by a predetermined load amount until a temperature of the SCR catalyst (60) reaches a predetermined temperature, wherein the predetermined load amount varies depending on a difference between the temperature of the SCR catalyst (60) and the predetermined temperature, and the greater the difference between the temperature of the SCR catalyst (60) and the predetermined temperature, the greater the predetermined load amount. [2] The vehicle control system according to claim 1, wherein the difference between the temperature of the SCR catalyst (60) and the predetermined temperature is divided into two or more temperature difference sections and the predetermined load amount is constant in any one temperature difference section. [3] The vehicle control system of claim 1, wherein when the engine (10) is running at cold start, the controller (80) determines whether an amount of a nitrogen oxide contained in the exhaust gas is greater than a reference amount, and when the amount of the nitrogen oxide contained in the exhaust gas is greater than the reference amount, the controller (80) controls the injection module (40) to inject a reducing agent in accordance with the amount of the nitrogen oxide. [4] The vehicle control system of claim 3, wherein the controller (80) controls the HSG (70) to generate at least a portion of a driver's demand torque before the reductant is injected. [5] A vehicle control method for using a vehicle control system with an engine (10) that generates energy by combusting an air-fuel mixture and emits exhaust gas generated during a combustion process of the air-fuel mixture, a hybrid starter / generator (HSG) (70) configured to start the engine (10) or generate electricity using energy generated in the engine (10), an injection module (40) that injects a reducing agent into the exhaust gas, a selective catalytic reduction (SCR) catalyst (60) that reduces nitrogen oxide contained in the exhaust gas using the reducing agent, and a controller (80) that controls operations of the engine (10), the injection module (40), and the HSG (70), the vehicle control method comprising the following steps: Determining (S310) a machine state when a cold start condition is met; Determining (S320) whether a temperature of the SCR catalyst (60) is lower than a first temperature when the engine (10) is in an idle state; and Increasing (S325) a load of the HSG (70) by a first load when the temperature of the SCR catalyst (60) is lower than the first temperature; and when the temperature of the SCR catalyst (60) is equal to or higher than the first temperature, Determining (S330) whether the temperature of the SCR catalyst (60) is higher than a second temperature; Increasing (S340) the load of the HSG (70) by a second load that is less than the first load when the temperature of the SCR catalyst (60) is equal to or lower than the second temperature; and Return to the determination (S320) of whether the temperature of the SCR catalyst (60) is lower than the first temperature. [6] The vehicle control method of claim 5, further comprising: when the temperature of the SCR catalyst (60) is higher than the second temperature, Return to the determination (S310) of the machine state. [7] The vehicle control method according to claim 5, further comprising: additional injection (S315) of fuel when the engine (10) is in an idling state. [8] A vehicle control method according to claim 5, further comprising: when the engine (10) is not operating in an idle state, Determining (S345) whether an amount of a nitrogen oxide contained in the exhaust gas is greater than a reference amount; Calculating (S355) a reducing agent injection amount according to the amount of nitrogen oxide when the amount of nitrogen oxide contained in the exhaust gas is greater than the reference amount; and Inject (S360) the reducing agent according to the calculated reducing agent injection quantity. [9] The vehicle control method according to claim 8, further comprising: when an amount of a nitrogen oxide contained in the exhaust gas is larger than the reference amount, Generating (S350) at least a certain portion of a driver's request torque by the HSG (70) before injecting a reducing agent.

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