Patent Publication Number: US-2017363017-A1

Title: Exhaust purification apparatus for internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on Japanese Patent Application No. 2015-029183 filed on Feb. 18, 2015, the disclosure of which is incorporated herein by reference. 
     Technical Field 
     The present disclosure relates to an exhaust purification apparatus for an internal combustion engine, the exhaust purification apparatus having an exhaust catalytic agent disposed in an exhaust passage. 
     Background Art 
     An exhaust purification catalytic agent for an internal combustion engine mounted in a vehicle or the like is disposed in an exhaust passage and reduces emissions included in exhaust gas. The exhaust purification catalytic agent generally exerts an exhaust purification performance when a temperature of the exhaust purification catalytic agent reaches a specified activation temperature. In other words, the exhaust purification catalytic agent cannot exert the exhaust purification performance sufficiently when the temperature of the exhaust purification catalytic agent is lower than the specified activation temperature. 
     Then, an exhaust purification apparatus described in Patent Literature 1 has a secondary air injection nozzle and a throttle valve. The secondary air injection nozzle is arranged upstream of an exhaust purification catalytic agent in an exhaust passage. The throttle valve is arranged downstream of the exhaust purification catalytic agent in the exhaust passage. The exhaust purification apparatus described in Patent Literature 1 activates the exhaust purification catalytic agent in a manner that the throttle valve is fully closed when a cooling operation for cooling an internal combustion engine is started and that an exhaust temperature is increased by supplying a secondary air from the secondary air injection nozzle. A temperature of the exhaust purification catalytic agent tends to be lower than an activation temperature during the cooling operation. 
     PRIOR ART LITERATURES 
     Patent Literature 
     Patent Literature 1: JP 2001-132436 A 
     SUMMARY OF INVENTION 
     According to studies conducted by the inventor of the present disclosure, an exhaust pressure increases as time proceeds, not increases immediately, when the throttle valve is fully open, according to the exhaust purification apparatus described in Patent Literature 1. As a result, the exhaust temperature and the temperature of the exhaust purification catalytic agent also increase as time proceeds. Therefore, a certain amount of time is required for increasing the temperature of the exhaust purification catalytic agent to the activation temperature, and thereby is it difficult to activate the exhaust purification catalytic agent promptly. 
     The present disclosure addresses the above-described issues, and it is an objective of the present disclosure to provide an exhaust purification apparatus for an internal combustion engine that can secure a reduction effect reducing emissions and that can increase a temperature of an exhaust purification catalytic agent promptly. 
     An exhaust purification apparatus for an internal combustion engine has an exhaust purification catalytic agent disposed in an exhaust passage. The exhaust purification apparatus for the internal combustion engine has an exhaust throttle valve, an actuator, and a controller. The exhaust throttle valve is arranged upstream of the exhaust purification catalytic agent in the exhaust passage and changes a passage sectional area of the exhaust passage. The actuator operates the exhaust throttle valve to be open and closed. The controller controls the exhaust throttle valve to be open and closed through the actuator. The controller decreases an opening degree of the exhaust throttle valve to narrow the passage sectional area of the exhaust passage upon a heating request for heating the exhaust purification catalytic agent. 
     According to the above-described configuration, exhaust gas flows to a part of the exhaust purification catalytic agent locally when the exhaust throttle valve narrows the passage sectional area of the exhaust passage. As a result, a temperature of the part of the exhaust purification catalytic agent increases promptly, thereby the exhaust purification catalytic agent can be activated promptly. In addition, most of the exhaust gas flows in an activated portion of the exhaust purification catalytic agent, and thereby a reduction effect reducing emissions can be secured. 
     Thus, according to the present disclosure, a temperature of the exhaust purification catalytic agent can be increased more promptly while securing the reduction effect reducing emissions. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. 
         FIG. 1  is a diagram illustrating a schematic configuration of an exhaust purification apparatus for an internal combustion engine according to an embodiment. 
         FIG. 2  is a cross-sectional view illustrating a peripheral structure of an exhaust purification catalytic agent according to the embodiment. 
         FIG. 3  is a flow chart illustrating a proceeding of a control for opening and closing an exhaust throttle valve operated by the exhaust purification apparatus. 
         FIG. 4  is a graph showing a flow speed distribution of exhaust gas flowing in an exhaust passage. 
         FIG. 5A  is a graph showing a temperature variation in the exhaust purification catalytic agent without the exhaust throttle valve. 
         FIG. 5B  is a graph showing a temperature variation in the exhaust purification catalytic agent when the exhaust throttle valve narrows a passage sectional area of the exhaust passage. 
         FIG. 5C  is a graph showing a temperature variation in the exhaust purification catalytic agent when the exhaust throttle valve further narrows the passage sectional area of the exhaust passage. 
         FIG. 6A  is a graph showing a temperature variation in the exhaust purification catalytic agent without the exhaust throttle valve  33 . 
         FIG. 6B  is a graph showing a temperature variation in the exhaust purification catalytic agent when the exhaust throttle valve narrows a passage sectional area of the exhaust passage. 
         FIG. 6C  is a graph showing a temperature variation in the exhaust purification catalytic agent when the exhaust throttle valve further narrows the passage sectional area of the exhaust passage. 
         FIG. 7  is a flow chart illustrating a proceeding of a control for opening and closing an exhaust throttle valve according to an another embodiment of the present disclosure. 
         FIG. 8  is a flow chart illustrating a proceeding of a control for opening and closing an exhaust throttle valve according to an another embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of an exhaust purification apparatus for an internal combustion engine will be described hereafter. The internal combustion engine of the present embodiment is a cylindrical injection engine.  FIG. 1  is a diagram illustrating a schematic configuration of the internal combustion engine of the present embodiment around a single cylinder. 
     As shown in  FIG. 1 , an internal combustion engine  1  of the present embodiment has a cylinder  10 , a piston  11 , a fuel injection valve  12 , a spark plug  13 , an intake valve  14 , and an exhaust valve  15 . 
     The piston  11  is housed in the cylinder  10  to reciprocate in the cylinder  10 . A space surrounded by the cylinder  10  and the piston  11  defines a combustion chamber  16 . 
     The fuel injection valve  12  is arranged to protrude into the combustion chamber  16 . A high-pressure fuel is supplied to the fuel injection valve  12  through a common rail (not shown). The fuel injection valve  12  injects the fuel into the combustion chamber  16 . The combustion chamber  16  is connected to an intake passage  20  through an intake port  17  provided in the cylinder  10 . The combustion chamber  16  is also connected to an exhaust passage  30  through an exhaust port  18  provided in the cylinder  10 . 
     The spark plug  13  is arranged to protrude into the combustion chamber  16 . The spark plug  13  ignites the fuel in the combustion chamber  16  when electrical power is applied to the spark plug  13 . 
     In the combustion chamber  16 , intake air introduced through the intake passage  20  and the intake port  17  and the fuel injected by the fuel injection valve  12  are mixed to be a mixed gas. The mixed gas generated in the combustion chamber  16  is combusted due to an ignition by the spark plug  13 . The piston  11  reciprocates in the cylinder  10  due to the combustion of the mixed gas. The reciprocation of the piston  11  is converted to a rotational movement of an engine output shaft S through a connecting rod  19 , thereby generating a power as the internal combustion engine. Exhaust gas generated by the combustion of the mixed gas is emitted through the exhaust port  18  and the exhaust passage  30 . 
     The intake valve  14  is arranged in the intake port  17 . The intake valve  14  opens and closes the intake port  17 . 
     The exhaust valve  15  is arranged in the exhaust port  18 . The exhaust valve  15  opens and closes the exhaust port  18 . 
     The internal combustion engine  1  has a throttle valve  21 , a throttle motor  22 , an intake air volume sensor  50 , and a throttle opening degree sensor  51  that are disposed in the intake passage  20 . The throttle valve  21  adjusts a volume of intake air introduced into the combustion chamber  16  by changing a passage sectional area of the intake passage  20 . The throttle motor  22  operates the throttle valve  21  to be open and closed. The intake air volume sensor  50  detects an intake air volume GA of the intake air introduced into the combustion chamber  16 . The throttle opening degree sensor  51  detects a throttle opening degree TA that is an opening degree of the throttle valve  21 . 
     The internal combustion engine  1  has an exhaust purification catalytic agent  31 , an exhaust throttle valve  33 , and an actuator  34  that are disposed in the exhaust passage  30 . 
     As shown in  FIG. 2 , the exhaust purification catalytic agent  31  is housed in a case  35  that configures a part of the exhaust passage  30 . The case  35  surrounds the exhaust purification catalytic agent  31 . The case  35  has a flange  350  and a flange  351  at both ends respectively. The flange  350  is fixed to a flange  400  of an upstream exhaust pipe  40  by a method such as bolting (not shown). The upstream exhaust pipe  40  is connected to the exhaust port  18  through an exhaust manifold (not shown). The flange  351  is fixed to a flange  410  of a downstream exhaust pipe  41  by a method such as bolting (not shown). In the following description, an opening portion of the flange  350 , which is an inlet of the case  35  from which the exhaust gas flows in, will be referred to as an exhaust inlet port  352 . 
     The case  35  has a large diameter portion  353  that enlarges a passage sectional area of the case  35 . The large diameter portion  353  is located in a center area of the case  35 . The exhaust purification catalytic agent  31  is housed in the large diameter portion  353 . The exhaust purification catalytic agent  31  may be a three-way catalytic agent. The exhaust purification catalytic agent  31  purifies the exhaust gas by oxidizing and reducing a toxic substance such as hydrocarbon, carbon monoxide, and nitrogen oxide included in the exhaust gas. 
     The exhaust throttle valve  33  is arranged adjacent to the exhaust inlet port  352  of the case  35 . That is, the exhaust throttle valve  33  is located upstream of the exhaust purification catalytic agent  31 . The exhaust throttle valve  33  changes a passage sectional area of the exhaust passage  30  by reciprocating between a closing position shown in the drawings and an opening position at which the exhaust throttle valve  33  fully opens the exhaust passage  30 . The closing position shown in the drawings is a position at which the exhaust throttle valve  33  narrows the passage sectional area of the exhaust passage  30  to define a single throttle path in a center area of the exhaust passage  30 . 
     The actuator  34  may be configured centering around a motor. The actuator  34  operates the exhaust throttle valve  33  to reciprocate between the closing position and the opening position. 
     As shown in  FIG. 1 , the internal combustion engine  1  has an accelerator opening degree sensor  53 , a water temperature sensor  54 , and an engine rotational speed sensor  55 . The accelerator opening degree sensor  53  detects an accelerator displacement amount AP that is an displacement amount of an accelerator of a vehicle when being pressed to the floor. The water temperature sensor  54  detects a cooling water temperature TW that is a temperature of cooling water cooling the internal combustion engine  1 . The engine rotational speed sensor  55  detects an engine rotational speed NE that is a rotational speed of the engine output shaft S. 
     The internal combustion engine  1  has an ECU (Electronic Control Unit)  60  as a controller that controls the fuel injection valve  12 , the spark plug  13 , the throttle motor  22 , and the actuator  34 . The ECU  60  is configured centering around a microcomputer and has CPU and a memory. Output signals from the intake air volume sensor  50 , the throttle opening degree sensor  51 , the accelerator opening degree sensor  53 , the water temperature sensor  54 , and the engine rotational speed sensor  55  are input to the ECU  60 . The ECU  60  obtains information regarding the intake air volume GA, the throttle opening degree TA, the acceleration displacement amount AP, the cooling water temperature TW, and the engine rotational speed sensor NE with a specified period based on the output signals from the sensors  50  to  55 . 
     The ECU  60  controls a fuel injection timing, a fuel injection volume, and the throttle opening degree TA by controlling the fuel injection valve  12 , the spark plug  13 , and the throttle motor  22  based on the intake air volume GA, the throttle opening degree TA, the acceleration displacement amount AP, and the engine rotational speed NE. 
     The ECU  60  changes a condition of the exhaust throttle valve  33  between an opening condition and a closed condition by controlling an operation of the actuator  34  based on the cooling water temperature TW and the acceleration displacement amount AR An exhaust purification apparatus  70  of the present embodiment is configured by the exhaust purification catalytic agent  31 , a floor temperature sensor  53 , the exhaust throttle valve  33 , the actuator  34 , and the ECU  60 . 
     A control for opening and closing the exhaust throttle valve  33  operated by the ECU  60  will be described hereafter referring to FIG,  3 . The ECU  60  performs a proceeding shown in  FIG. 3  in a specified period. The exhaust throttle valve  33  is in the opening condition when the proceeding shown in  FIG. 3  starts. 
     As shown in  FIG. 3 , the ECU  60  determines whether a heating request for heating the exhaust purification catalytic agent  31  is made (at S 1 ). For example, the ECU  60  determines whether the cooling water temperature TW is lower than or equal to a water temperature threshold TWth when the internal combustion engine  1  starts to operate, and determines that a cooling operation cooling the internal combustion engine  1  is being performed when the cooling water temperature TW is lower than or equal to the water temperature threshold TWth. The water temperature threshold TWth is set in advance, e.g., based on experimental results, such that it can be determined whether a temperature of the internal combustion engine  1  is a temperature for starting the cooling operation. The ECU  60  determines that the heating request heating for the exhaust purification catalytic agent  31  is made when the cooling operation cooling the internal combustion engine  1  is being performed (S 1 : YES). On the other hand, the ECU  60  determines that the heating request for heating the exhaust purification catalytic agent  31  is not made when any one of the following condition (a1) to (a3) is met (S 1 : NO). 
     (a1) The cooling water temperature TW is higher than the water temperature threshold TWth. 
     (a2) A specified time has elapsed since the cooling operation cooling the internal combustion engine  1  is started. 
     (a3) An integrated value of the intake air volume GA from starting the cooling operation cooling the internal combustion engine  1  is higher than a specified volume. 
     The ECU  60  keeps the exhaust throttle valve  33  to be in the opening condition (at S 4 ) when the heating request for heating the exhaust purification catalytic agent  31  is not made (S 1 : NO). 
     The ECU  60  decreases an opening degree of the exhaust throttle valve  33  (at S 2 ) when the heating request for heating the exhaust purification catalytic agent  31  is made (S 1 : YES). Then, the ECU  60  determines whether an acceleration request is made (at S 3 ). Specifically, the ECU  60  determines that the acceleration request is made (S 3 : YES) when the acceleration displacement amount AP is greater than or equal to a specified threshold APth. The ECU  60  returns to a determination process of S 2  when it is determined that the acceleration request is not made (S 3 : NO). Accordingly, the exhaust throttle valve  33  is kept in the closing condition when the heating request for heating the exhaust purification catalytic agent  31  is made (S 1 : YES) and when the acceleration request is not made (S 3 : NO). 
     The ECU  60  changes a condition of the exhaust throttle valve  33  from the closing condition to the opening condition (at S 4 ) when the heating request for heating the exhaust purification catalytic agent  31  is not made (S 1 : NO) or when the acceleration request is made (S 3 : YES) while the exhaust throttle valve  33  is in the closing condition. 
     An example of an operation of the exhaust purification apparatus  70  of the present embodiment will be described hereafter. 
     The ECU  60  operates the exhaust throttle valve  33  to be in the closing condition shown in  FIG. 2  when the heating request for heating the exhaust purification catalytic agent  31  is made. Accordingly, most of the exhaust gas flows in the center portion of the exhaust passage  30 .  FIG. 4  shows a flow velocity distribution of the exhaust gas. A two-dot chain line shows the flow velocity distribution without the exhaust throttle valve  33 . A one-dot chain line shows the flow velocity distribution when the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  to have a diameter A. A solid line shows the flow velocity distribution when the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  to have a diameter B that is smaller than the diameter A. In  FIG. 4 , a horizontal axis shows a distance from the center portion of the exhaust passage  30  shown in  FIG. 1  in a radial direction, and a vertical axis shows a flow velocity v of the exhaust gas. 
     As shown in  FIG. 4 , the flow velocity v of the exhaust gas is the fastest in the center portion of the exhaust passage  30  and slows toward an outer periphery of the exhaust passage  30  regardless of a presence or absence of the exhaust throttle valve  33 . The flow velocity v of the exhaust gas in the center portion of the exhaust passage  30  becomes faster in a case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  as compared to a case that the exhaust throttle valve  33  is omitted. Moreover, the flow velocity v of the exhaust gas becomes faster as the passage sectional area of the exhaust passage  30  decreases. Thus, it is found that the flow velocity v of the exhaust gas can be increased in the center portion of the exhaust passage  30  in a manner that the exhaust throttle valve  33  is set to be in the closing condition so as to decrease the passage sectional area of the exhaust passage  30 . A temperature of the exhaust purification catalytic agent  31  can be increased more promptly by increasing the flow velocity v of the exhaust gas in the center portion of the exhaust passage  30 , as compared to the case that the exhaust throttle valve  33  is omitted. 
       FIG. 5A  to  FIG. 5C  show variations of the temperature of the exhaust purification catalytic agent  31  at positions P 10  to P 12  shown in  FIG. 2 . A two-dot chain line shows the variations in the case that the exhaust throttle valve  33  is omitted. A one-dot chain line shows the variations in the case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  to have the diameter A. A solid line shows the variations in the case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  to have the diameter B that is smaller than the diameter A. As shown in  FIG. 2 , the positions P 10  to P 12  are located on a central axis ml of the exhaust purification catalytic agent  31 . The position P 10  is a position of an end surface  310  of the exhaust purification catalytic agent  31  on an exhaust inlet side. The position P 11  is a position of a center of the exhaust purification catalytic agent  31 . The position P 12  is a position of an end surface  311  of the exhaust purification catalytic agent  31  on an exhaust outlet side. 
       FIG. 6A  to  FIG. 6C  show variations of the temperature of the exhaust purification catalytic agent  31  at positions P 20  to P 22  shown in  FIG. 2 . A two-dot chain line shows the variations in the case that the exhaust throttle valve  33  is omitted. A one-dot chain line shows the variations in the case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  to have the diameter A. A solid line shows the variations in the case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  to have the diameter B that is smaller than the diameter A. As shown in  FIG. 2 , the positions P 20  to P 22  are located on a line m 2  extending along the outer periphery of the exhaust purification catalytic agent  31 . The position P 20  is a position of the end surface  310  of the exhaust purification catalytic agent  31  on the exhaust inlet side. The position P 21  is a position of a center of the exhaust purification catalytic agent  31 . The position P 22  is a position of the end surface  311  of the exhaust purification catalytic agent  31  on the exhaust outlet side. 
     As shown in  FIG. 5A  to  FIG. 5C , the temperature of the exhaust purification catalytic agent  31  along the central axis ml increases more promptly in the case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  as compared to the case that the exhaust throttle valve  33  is omitted. In addition, the temperature of the exhaust purification catalytic agent  31  increases more promptly as the passage sectional area of the exhaust passage  30  decreases. Therefore, a portion of the exhaust purification catalytic agent  31  along the central axis ml can be activated locally when a heating operation for heating the internal combustion engine  1 , in which the exhaust throttle valve  33  is set to be in the closing condition, is requested. On this occasion, most of the exhaust gas flows in the portion of the exhaust purification catalytic agent  31  along the central axis m 1 , thereby a reduction effect reducing emissions can be secured. 
     On the other hand, as shown in  FIG. 6A  to  FIG. 6C , the temperature of the outer periphery of the exhaust purification catalytic agent  31  increases hardly in the case that the exhaust throttle valve  33  decreases the passage sectional area of the exhaust passage  30  as compared to the case that the exhaust throttle valve  33  is omitted. In addition, the temperature of the outer periphery of the exhaust purification catalytic agent  31  increases harder as the passage sectional area of the exhaust passage  30  decreases. As a result, the reduction effect reducing the emissions deteriorates in the outer periphery of the exhaust purification catalytic agent  31 . However, a flow rate of the exhaust gas flowing in the outer periphery of the exhaust purification catalytic agent  31  is small since most of the exhaust gas flows in the portion of the exhaust purification catalytic agent  31  along the central axis m 1 . Therefore, even when the reduction effect reducing the emissions deteriorates in the outer periphery of the exhaust purification catalytic agent  31 , the deterioration have less affect, and the reduction effect reducing the emissions in the portion of the exhaust purification catalytic agent  31  along the central axis m 1  can have a predominantly greater affect. Moreover, the temperature of the outer periphery of the exhaust purification catalytic agent  31  increases as time elapses as shown in  FIG. 6A  to  FIG. 6C , since reaction heat generated by a catalytic reaction of the exhaust purification catalytic agent  31  in the portion along the central axis m 1  transmits to the outer periphery of the exhaust purification catalytic agent  31 . As a result, the temperature of the outer periphery of the exhaust purification catalytic agent  31  reaches the activation temperature. 
     According to the exhaust purification apparatus  70  of the above-described embodiment, the following operations and effects (1) through (5) can be obtained. 
     (1) The portion of the exhaust purification catalytic agent  31  along the central axis m 1  can be activated more promptly when the heating request for heating the exhaust purification catalytic agent  31  is made. In addition, the reduction effect reducing the emissions can be secured since most of the exhaust gas flows in the portion of the exhaust purification catalytic agent  31  along the central axis m 1  after the portion is activated. 
     (2) The ECU  60  determines the heating request for heating the exhaust purification catalytic agent  31  is made when the cooling operation cooling the internal combustion engine  1  is being performed, and decreases the opening degree of the exhaust throttle valve  33 . Accordingly, a time required for activating the exhaust purification catalytic agent  31  can be shortened, specifically when the cooling operation cooling the internal combustion engine  1 , in which the exhaust purification catalytic agent  31  is needed to be activated promptly, is being performed. Thus, the reduction effect reducing the emissions can be excellent. 
     (3) When a driver operates the accelerator to accelerate the vehicle while the exhaust throttle valve  33  is in the closing condition, an exhaust pressure increases excessively, and an output power of the internal combustion engine  1  may deteriorate. According to the exhaust purification apparatus  70  of the present embodiment, the ECU  60  determines that the acceleration request is made and changes the condition of the exhaust throttle valve  33  from the closing condition to the opening condition when the driver operates the accelerator to accelerate the vehicle. Therefore, the deterioration of the output power from the internal combustion engine  1  due to an excess increase of the exhaust pressure can be suppressed. As a result, a deterioration of drivability can be suppressed. 
     (4) The exhaust throttle valve  33  defines the single throttle passage in the exhaust passage  30  when being in the closing condition. Specifically, the exhaust throttle valve  33  defines the single throttle path in the center area of the exhaust passage. Accordingly, the flow velocity of the exhaust gas increases, thereby the temperature of the exhaust purification catalytic agent  31  can be increased more promptly as compared to a case that more than one throttle path are defined. That is, a time required for activating the exhaust purification catalytic agent  31  can be further shortened, and thereby the reduction effect reducing the emissions can be obtained accurately. 
     (5) The exhaust throttle valve  33  is arranged adjacent to the exhaust inlet port  352  of the case  35 . Accordingly, the exhaust gas of which flow velocity is increased by the exhaust throttle valve  33  can reach the exhaust purification catalytic agent  31  easily, and thereby the portion of the exhaust purification catalytic agent  31  along the central axis ml can be activated easily. 
     (Other Modifications) 
     While the present disclosure has been described with reference to preferred embodiments thereof, it is to be understood that the disclosure is not limited to the preferred embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements within a scope of the present disclosure. 
     As shown in  FIG. 7 , the ECU  60  may determine whether the intake air volume GA detected by the intake air volume sensor  50  is greater than or equal to a specified volume (at S 30 ), instead of the process of S 3  shown in  FIG. 3 . Alternatively, as shown in  FIG. 1 , an exhaust flow rate sensor  36  that detects a flow rate GB of the exhaust gas may be disposed in the exhaust passage  30 . As shown in  FIG. 8 , the ECU  60  may determine whether the flow rate GB of the exhaust gas detected by the exhaust flow rate sensor  36  is greater than or equal to a specified value (at S 31 ), instead of the process of S 3  shown in  FIG. 3 . The intake air volume GA or the flow rate GB of the exhaust gas is increased when the driver operates the accelerator to accelerate the vehicle. That is, according to both the processing shown in  FIG. 7  and the processing shown in  FIG. 8 , the condition of the exhaust throttle valve  33  is changed from the closing condition to the opening condition when the driver operates the accelerator to accelerate the vehicle. Therefore, the same operations and effects as the above-described operations and effects (3) can be obtained. 
     A determination process at S 1  in  FIG. 3  for determining whether the heating request for heating the exhaust purification catalytic agent  31  is made can be modified as required. For example, as shown in  FIG. 1 , an exhaust temperature sensor  57  that detects an exhaust temperature TO of the exhaust gas after passing through the exhaust purification catalytic agent  31  may be disposed in the exhaust passage  30 . Then, the ECU  60  may determine that the heating request for heating the exhaust purification catalytic agent  31  is made when the exhaust temperature TO that is detected by the exhaust temperature sensor  57  is lower than a specified temperature. Alternatively, the ECU  60  may calculate an estimated temperature of the exhaust purification catalytic agent  31  based on a variation of the exhaust temperature TO detected by the exhaust temperature sensor  57 , and may determine that the heating request for heating the exhaust purification catalytic agent  31  is made when the estimated temperature is lower than a specified temperature. 
     The exhaust throttle valve  33  is not limited to be arranged adjacent to the exhaust inlet port  352  of the case  35 . However, a position of the exhaust throttle valve  33  can be changed as required as long as the exhaust throttle valve  33  is located upstream of the exhaust purification catalytic agent  31 . 
     The exhaust throttle valve  33  may define more than one throttle path in the exhaust passage  30  when being in the closing condition. Alternatively, the exhaust throttle valve  33  may define the throttle path outside the center area of the exhaust passage  30  when being in the closing condition. 
     However, the present disclosure is not limited to the above-described specific examples. That is, modifications that are made by a person having ordinary skill in the art, as required, based on the specific examples are included in a range of the present disclosure as long as having the features of the present disclosure. For example, elements mentioned in the specific examples, an arrangement, a material, a condition, a shape, a size, etc. of the elements are not limited to the specific examples, and can be changed as required. Elements mentioned in the above-described embodiments can be combined as long as it is technically possible, and the combination is included in the range of the present disclosure as long as having the features of the above-described embodiments.