JP2013007336A - Reformed gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reformed gas recirculation device capable of properly controlling a temperature of a reforming catalyst and stably supplying reformed gas.SOLUTION: In a reformed gas recirculation device 100 recirculating reformed gas into an intake system comprises: a first exhaust passage 31; a second exhaust passage 32 merging with the first exhaust passage 31; an exhaust purifying unit 40 provided at the first exhaust passage 31; a fuel supply part 53 supplying fuel into the second exhaust passage 32; an exhaust reforming unit 50 having a purification catalyst capable of purifying exhaust and a reforming catalyst capable of generating reformed gas from the exhaust flowing through the second exhaust passage 32 and the fuel supplied from the fuel supply part 53; a communication passage 55 branching from the second exhaust passage 32 downstream of the exhaust reforming unit 50 and communicating with the intake system; a regulation valve 54 capable of regulating a flow rate of the exhaust flowing in the second exhaust passage 32; a switching valve 56 capable of switching a gas passage of the second exhaust passage 32 to the first exhaust passage 31 side or the communication passage 55 side; and a control part 60 controlling the regulation valve 54 and the switching valve 56.

Description

  The present invention relates to a reformed gas recirculation device capable of recirculating reformed gas to an intake system of an engine.

  In Patent Document 1, fuel is supplied to exhaust gas discharged from an engine, a mixture of exhaust gas and fuel is reformed into a reformed gas containing hydrogen by a reforming catalyst, and the reformed gas is recirculated to an intake passage. A reformed gas reflux apparatus is disclosed. By recirculating the reformed gas to the intake system in this way, the combustibility of the air-fuel mixture in the engine can be improved. Other related literature inventions include the invention described in Patent Document 2.

JP 2006-37879 A JP 2007-332891 A

  However, in the reformed gas recirculation device described in Patent Document 1, an exhaust reforming unit is installed in the exhaust passage between the engine and the exhaust purification catalyst, and almost all the exhaust discharged from the engine is exhausted from the exhaust reforming unit. There is a problem that the temperature of the reforming catalyst provided in the exhaust reforming unit is likely to vary depending on the engine operating state. For example, when high-temperature exhaust is discharged from the engine at full load or the like, the reforming catalyst becomes too high and may be thermally deteriorated.

  Therefore, the present invention has been made paying attention to such problems, and provides a reformed gas recirculation device that can appropriately control the temperature of the reforming catalyst and can stably supply the reformed gas. Objective.

  The reformed gas recirculation device of the present invention is configured to generate a reformed gas containing hydrogen from exhaust discharged from an engine and flowing through an exhaust passage, and to recirculate the reformed gas to an intake system. The reformed gas recirculation device includes a first exhaust passage through which the exhaust discharged from the engine flows, a second exhaust passage through which the exhaust discharged from the engine flows and merges with the first exhaust passage on the downstream side, and a second exhaust An exhaust purification unit having a purification catalyst capable of purifying exhaust, provided in a first exhaust passage upstream of the joining portion where the passages merge, a fuel supply unit for supplying fuel into the second exhaust passage, and a second exhaust An exhaust gas reforming unit provided in the passage and having a reforming catalyst capable of purifying exhaust gas, an exhaust gas flowing through the second exhaust passage and a reforming catalyst capable of generating reformed gas from the fuel supplied from the fuel supply unit; And a communication passage that branches off from the second exhaust passage downstream of the quality unit and communicates with the intake system. Further, the reformed gas recirculation device includes an adjustment valve capable of adjusting an exhaust flow rate of the exhaust gas flowing through the second exhaust passage, and a switching valve capable of switching the gas path of the second exhaust passage to the first exhaust passage side or the communication passage side. And a control unit for controlling the adjusting valve and the switching valve.

  According to the present invention, the control valve controls the adjustment valve that adjusts the exhaust flow rate of the second exhaust passage and the switching valve that switches the gas path of the second exhaust passage, so that the temperature of the reforming catalyst can be appropriately controlled and improved. It becomes possible to stably supply quality gas to the engine.

1 is a schematic configuration diagram of a reformed gas recirculation device for an engine according to a first embodiment of the present invention. It is a flowchart which shows the reformed gas recirculation | reflux control which a controller performs. It is a figure which shows the relationship between reforming catalyst temperature and the opening degree of a switching valve and an adjustment valve. It is an engine speed-load map regarding recirculation | reflux of reformed gas. It is a schematic block diagram of the reformed gas recirculation apparatus of the engine by 2nd Embodiment of this invention. It is a flowchart explaining the reformed gas recirculation | control which a controller performs. It is a schematic block diagram of the reformed gas recirculation apparatus which concerns on the modification of 2nd Embodiment. It is an engine speed-load map regarding the recirculation | reflux of the reformed gas used in the reformed gas recirculation apparatus which concerns on the modification of 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
With reference to FIG. 1, the structure of the reformed gas recirculation apparatus 100 by 1st Embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram of a reformed gas recirculation device 100 that recirculates reformed gas to an intake system of an engine 10 for a vehicle.

  As shown in FIG. 1, the reformed gas recirculation device 100 includes an in-line four-cylinder engine 10, an intake passage 20 that guides intake air taken in from the outside to the engine 10, and exhaust gas that guides exhaust exhausted from the engine 10 to the outside. And a passage 30.

  The engine 10 includes a cylinder head 11 disposed on the upper part of the cylinder block. An intake port 12 and an exhaust port 13 are formed in the cylinder head 11 for each cylinder. Two intake ports 12 are provided for one cylinder, and these two intake ports 12 are formed so as to merge on the upstream side in the intake flow direction. Further, two exhaust ports 13 are provided for one cylinder, and these two exhaust ports 13 are formed so as to merge on the downstream side in the exhaust flow direction.

  Each intake port 12 is provided with an intake valve 14, and each exhaust port 13 is provided with an exhaust valve 15. The intake valve 14 is driven by an intake cam formed on the intake camshaft, and opens and closes the intake port 12 at a predetermined timing according to the vertical movement of the piston. The exhaust valve 15 is driven by an exhaust cam formed on the exhaust camshaft, and opens and closes the exhaust port 13 at a predetermined timing according to the vertical movement of the piston.

  The intake passage 20 distributes intake air taken from the outside to each cylinder via the intake manifold 21 and guides intake air to the intake port 12 of each cylinder. The intake manifold 21 is provided with a fuel injection valve (not shown) that injects fuel into the intake passage 20.

  When the mixture of intake air and fuel burns in the cylinder of the engine 10, exhaust is discharged from the engine 10. The exhaust is discharged to the outside through the exhaust port 13 and the exhaust passage 30. The exhaust passage 30 branches at an upstream position of the first exhaust passage, an exhaust manifold 33 that joins the exhaust discharged from the exhaust port 13 and guides it downstream, a first exhaust passage 31 connected to the downstream end of the exhaust manifold 33, and the first exhaust passage. And a second exhaust passage 32 that merges at a downstream position.

  The first exhaust passage 31 is a passage that guides the exhaust discharged from the engine 10 to the outside. An exhaust purification unit 40 that can purify the exhaust is installed in the first exhaust passage 31. The exhaust purification unit 40 is a catalytic converter in which a three-way catalyst is supported on a carrier. The three-way catalyst of the exhaust purification unit 40 purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust flowing in the first exhaust passage 31.

  The second exhaust passage 32 is a passage that branches from the first exhaust passage 31 upstream of the exhaust purification unit 40 and merges with the first exhaust passage 31 downstream of the exhaust purification unit 40. An exhaust gas reforming unit 50 that can purify and reform exhaust gas is installed in the second exhaust passage 32. A fuel supply unit 53 that can supply fuel such as gasoline into the second exhaust passage 32 is installed in the second exhaust passage 32 upstream of the exhaust reforming unit 50.

  The exhaust reforming unit 50 includes a purifying unit 51 that can purify exhaust and a reforming unit 52 that can reform exhaust. The purifying unit 51 is a catalytic converter in which a three-way catalyst is supported on a carrier, and the reforming unit 52 is a catalytic converter in which a reforming catalyst is supported on a carrier. In this embodiment, the purification unit 51 is arranged on the upstream side of the reforming unit 52, but the reforming unit 52 may be arranged on the upstream side of the purification unit 51.

  The three-way catalyst of the purification unit 51 purifies HC, CO, and NOx contained in the exhaust flowing through the second exhaust passage.

  The reforming catalyst of the reforming unit 52 reforms the air-fuel mixture formed from the exhaust gas flowing through the second exhaust passage 32 and the fuel supplied by the fuel supply unit 53 into a reformed gas containing hydrogen. The reforming unit 52 is provided with a temperature sensor 52A for detecting the temperature of the reforming catalyst. Since it is difficult to directly detect the reforming catalyst temperature, the temperature sensor 52A detects the temperature of the carrier carrying the reforming catalyst. The reforming catalyst temperature may be estimated from the engine operating state, the exhaust temperature, and the like.

  An adjusting valve 54 for adjusting the flow rate of the exhaust gas flowing into the second exhaust passage 32 is installed in the second exhaust passage 32 upstream of the fuel supply unit 53. The flow rate of the exhaust gas flowing through the second exhaust passage 32 is adjusted by changing the opening degree of the adjustment valve 54.

  A communication passage 55 that communicates the second exhaust passage 32 and the intake passage 20 is provided in the second exhaust passage 32 downstream of the exhaust reforming unit 50. A cooler capable of cooling the reformed gas flowing through the communication path 55 may be installed in the communication path 55.

  A switching valve 56 is installed at a branch portion of the second exhaust passage 32 where the communication passage 55 branches. The switching valve 56 is a valve that can switch the gas path of the second exhaust passage 32 to the first exhaust passage 31 side or the communication passage 55 side.

  The adjustment valve 54, the switching valve 56, the fuel supply unit 53, and the like are controlled by the controller 60. The controller 60 is constituted by a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 60 may be composed of a plurality of microcomputers.

  The controller 60 includes a temperature sensor 52A that detects the reforming catalyst temperature, a crank angle sensor 61 that generates a crank angle signal for each predetermined crank angle of the engine 10, and an accelerator pedal that detects the amount of depression of an accelerator pedal included in the vehicle. Detection data from the sensor 62 or the like is input as a signal. The crank angle signal is used as a signal representing the engine speed of the engine 10. The depression amount of the accelerator pedal is used as a signal representative of the load of the engine 10.

  The controller 60 adjusts the opening degree of the adjustment valve 54 and the switching valve 56 based on the input signal and the like, and adjusts the amount of fuel supplied by the fuel supply unit 53.

  Next, the reformed gas recirculation control by the controller 60 will be described with reference to FIG. FIG. 2 is a flowchart for explaining the reformed gas recirculation control executed by the controller 60. This control is performed together with the start of engine operation, and is repeatedly executed at regular intervals, for example, at a period of 10 milliseconds.

  In S101, the controller 60 determines whether or not the reforming catalyst temperature T detected by the temperature sensor 52A is greater than a preset reference temperature T1. The reference temperature T1 is set to a temperature at which the reforming catalyst of the reforming unit 52 is activated.

  The controller 60 executes the process of S102 when the reforming catalyst temperature T is lower than the reference temperature T1, and executes the process of S104 when the reforming catalyst temperature T is higher than the reference temperature T1.

  In S102, the controller 60 controls the switching valve 56 so as to close the communication path 55. When the reforming catalyst temperature T is lower than the reference temperature T1, the communication path 55 is closed by the switching valve 56 as shown in FIG. 3A, and the gas path of the second exhaust path 32 is changed to the first exhaust path 31. Set to the side.

  In S103, the controller 60 sets the opening degree of the regulating valve 54 based on the reforming catalyst temperature T detected by the temperature sensor 52A. When the reforming catalyst temperature T is lower than the reference temperature T1, as shown in FIG. 3B, the opening degree of the regulating valve 54 is set so as to increase as the reforming catalyst temperature decreases.

  When the reforming catalyst temperature T is lower than the reference temperature T1, the regulating valve 54 is controlled so that the exhaust flow rate in the second exhaust passage 32 increases as the reforming catalyst temperature becomes lower. The switching valve 56 is controlled so that the gas path is on the first exhaust passage 31 side. As a result, the exhaust gas easily flows into the second exhaust passage 32 from the first exhaust passage 31, and the exhaust gas flowing through the second exhaust passage 32 is purified by the purification unit 51, and the temperature of the reforming catalyst of the reforming unit 52 is raised. After that, it flows into the first exhaust passage 31 again. Thus, by increasing the exhaust flow rate in the second exhaust passage 32, the reforming catalyst of the reforming unit 52 can be activated early after the engine 10 is started.

  Note that the exhaust gas flowing into the first exhaust passage 31 from the second exhaust passage 32 is discharged to the outside together with the exhaust purified by the exhaust purification unit 40 of the first exhaust passage 31.

  On the other hand, when it is determined in S101 that the reforming catalyst temperature T is higher than the reference temperature T1, the controller 60 determines in S104 that the current engine operating state is an operating state (reforming EGR) in which the reformed gas is circulated. It is determined whether or not the operation state is in effect. This determination is made by referring to the engine rotation speed-load map of FIG. 4 based on the engine rotation speed detected by the crank angle sensor 61 and the load detected by the accelerator pedal sensor 62.

  FIG. 4 is a diagram illustrating an example of an engine rotation speed-load map. As shown in FIG. 4, the low-load operation region A is a region where the reformed gas is circulated and the reformed EGR rate calculated as the ratio of the reformed gas in the intake air is maximized. It is. The medium load operation region B is a region in which the reformed gas is recirculated and the reforming EGR rate is set smaller than the operation region A. The high load operation region C is a region in which the reformed gas is recirculated and the reforming EGR rate is set smaller than the operation region B. The maximum load operation region D is a region where the reformed gas is not refluxed.

  In S104 of FIG. 2, when it is determined that the engine 10 is operating in the operation region A to C and is in the reformed EGR execution operation state, the controller 60 executes the process of S105. On the other hand, when it is determined that the engine 10 is operating in the operation region D and is not in the reforming EGR execution operation state, the controller 60 executes the process of S107.

  In S105, the controller 60 controls the switching valve 56 to open the communication path 55. When the reformed gas is recirculated, the communication passage 55 is opened by the switching valve 56 as shown in FIG. 3A, and the gas path of the second exhaust passage 32 is set to the communication passage 55 side.

  In S106, the controller 60 sets the opening of the adjustment valve 54 to a predetermined opening based on the reforming EGR rate set for each of the operation regions A to C in FIG. As the reforming EGR rate increases, the opening degree of the regulating valve 54 is set larger.

  When the reforming catalyst temperature T is higher than the reference temperature T1 and the reforming gas is recirculated, an amount of fuel corresponding to the reforming EGR rate is supplied into the exhaust in the second exhaust passage 32. Then, the fuel supply unit 53 is controlled, the opening degree of the adjustment valve 54 is set so that the exhaust flow rate corresponds to the reforming EGR rate, and the gas path of the second exhaust passage 32 is set to the communication passage 55 side. As a result, the mixture of exhaust gas and fuel is reformed into reformed gas containing hydrogen in the reforming unit 52, and the reformed gas is recirculated to the intake passage 20 through the communication passage 55. Thus, by recirculating the reformed gas containing hydrogen, which has a higher combustion speed than fuel such as gasoline, to the intake system, the combustibility of the air-fuel mixture in the engine 10 can be improved, and the lean combustion limit etc. can be expanded. It becomes.

  If it is determined in S104 that the reforming EGR execution operation state is not set, the controller 60 controls the switching valve 56 so as to close the communication path 55 in S107. By closing the communication passage 55 by the switching valve 56, the gas path of the second exhaust passage 32 is set to the first exhaust passage 31 side. In S108, the controller 60 sets the opening degree of the regulating valve 54 to a predetermined opening degree set in advance.

  When the engine 10 is operating in the operation region D and the recirculation of the reformed gas is not performed, the exhaust gas that has flowed into the second exhaust passage 32 passes through the purification unit 51 and the reforming unit 52 and again becomes the first. It flows into the exhaust passage 31 and is discharged to the outside together with the exhaust purified by the exhaust purification unit 40 of the first exhaust passage 31.

  After the process of S106 or S108, the controller 60 executes the process of S109. In S109, the controller 60 determines whether or not the reforming catalyst temperature T is higher than the upper limit temperature T2. The upper limit temperature T2 is a temperature set from the viewpoint of preventing thermal degradation of the reforming catalyst, and is set to a value higher than the reference temperature T1.

  When the reforming catalyst temperature T is lower than the upper limit temperature T2, the controller 60 ends the reformed gas recirculation control. On the other hand, when the reforming catalyst temperature T is higher than the upper limit temperature T2, the controller 60 executes the processing after S110.

  In S110, the controller 60 sets the opening degree of the regulating valve 54 based on the reforming catalyst temperature T detected by the temperature sensor 52A. When the reforming catalyst temperature T is higher than the upper limit temperature T2, as shown in FIG. 3B, the opening degree of the regulating valve 54 is set so as to decrease as the reforming catalyst temperature increases.

  In S111, the controller 60 controls the switching valve 56 so as to close the communication path 55, and ends the reformed gas recirculation control. When the reforming catalyst temperature T is higher than the upper limit temperature T2, the communication passage 55 is closed by the switching valve 56 as shown in FIG. 3A, and the gas path of the second exhaust passage 32 is changed to the first exhaust passage 31. Set to the side.

  When the reforming catalyst temperature T is higher than the upper limit temperature T2, the regulating valve 54 is controlled so that the exhaust flow rate in the second exhaust passage 32 decreases as the reforming catalyst temperature becomes higher. The switching valve 56 is controlled so that the gas path is on the first exhaust passage 31 side. This makes it difficult for exhaust to flow from the first exhaust passage 31 to the second exhaust passage 32, and prevents the temperature of the reforming catalyst in the reforming part 52 from rising too much, thereby preventing thermal deterioration of the reforming catalyst. Is possible. Note that the exhaust gas flowing into the first exhaust passage 31 from the second exhaust passage 32 is discharged to the outside together with the exhaust purified by the exhaust purification unit 40 of the first exhaust passage 31.

  In the reformed gas recirculation apparatus 100 according to the first embodiment described above, the following effects can be obtained.

  In the reformed gas recirculation device 100, the adjustment valve 54 is provided in the second exhaust passage 32 upstream of the exhaust reforming unit 50, and the switching valve 56 is provided in the branch portion of the second exhaust passage 32 where the communication passage 55 branches. By controlling the adjusting valve 54 and the switching valve 56, the temperature of the reforming catalyst can be appropriately controlled, and the reformed gas can be stably supplied to the engine 10.

  Only when the reformed gas is recirculated, the switching valve 56 is opened and the gas path of the second exhaust passage 32 is set to the communication path 55 side. Therefore, the reformed gas is always present in the communication path 55, and the reformed gas is present. The responsiveness of the reflux control can be improved.

(Second Embodiment)
With reference to FIG. 5, the reformed gas recirculation apparatus 100 by 2nd Embodiment of this invention is demonstrated. FIG. 5 is a schematic configuration diagram of the reformed gas recirculation apparatus 100 according to the second embodiment.

  The reformed gas recirculation device 100 according to the second embodiment has substantially the same configuration as that of the reformed gas recirculation device according to the first embodiment, but the configuration of the first exhaust passage 31 and the second exhaust passage 32 and the exhaust valve 15 The difference is that the exhaust flow rate in the second exhaust passage 32 is adjusted. Hereinafter, the difference will be mainly described.

  Two exhaust ports 13 provided for each cylinder are configured to flow exhaust gas independently of each other. Among the pair of exhaust ports 13 provided in one cylinder, the exhaust port 13 positioned on the upper side in FIG. 5 is provided with an exhaust valve 15 whose opening / closing timing and lift amount can be changed by the variable valve device 70. The variable valve operating device 70 is a known variable valve operating device disclosed in JP 2010-275932 A or the like.

  The first exhaust passage 31 is connected to the downstream end of the exhaust manifold 33A that collects the exhaust discharged from each exhaust port 13 provided with the exhaust valve 15 whose lift state cannot be changed.

  The second exhaust passage 32 is connected to the downstream end of the exhaust manifold 33B that collects the exhaust discharged from each exhaust port 13 provided with the exhaust valve 15 capable of changing the lift state. The downstream end of the second exhaust passage 32 is connected to the first exhaust passage 31 on the downstream side of the exhaust purification unit 40.

  In the second embodiment, no adjustment valve is installed in the second exhaust passage 32, and the exhaust flow rate in the second exhaust passage 32 is controlled by controlling the valve opening timing of the exhaust valve 15 by the variable valve operating device 70. To be adjusted. Thus, the exhaust valve 15 controlled by the variable valve operating device 70 plays a role as the regulating valve of the first embodiment.

  Next, the reformed gas recirculation control by the controller 60 will be described with reference to FIG. FIG. 6 is a flowchart for explaining the reformed gas recirculation control executed by the controller 60. This control is performed together with the start of engine operation, and is repeatedly executed at regular intervals, for example, at a period of 10 milliseconds.

  In S201, the controller 60 determines whether or not the reforming catalyst temperature T detected by the temperature sensor 52A is higher than a preset reference temperature T1. The reference temperature T1 is set to a temperature at which the reforming catalyst of the reforming unit 52 is activated.

  The controller 60 executes the process of S202 when the reforming catalyst temperature T is lower than the reference temperature T1, and executes the process of S204 when the reforming catalyst temperature T is higher than the reference temperature T1.

  In S202, the controller 60 controls the switching valve 56 so as to close the communication path 55. As a result, the gas path of the second exhaust passage 32 is set on the first exhaust passage 31 side.

  In S203, the controller 60 sets the valve opening timing (EVO timing) of the exhaust valve 15 controlled by the variable valve operating system 70 to a predetermined timing based on the reforming catalyst temperature T. When the reforming catalyst temperature T is lower than the reference temperature T1, the valve opening timing of the exhaust valve 15 is controlled to advance as the reforming catalyst temperature decreases. The exhaust valve 15 is closed at a predetermined timing regardless of the reforming catalyst temperature T.

  When the reforming catalyst temperature T is lower than the reference temperature T1, the exhaust valve 15 is controlled so that the exhaust flow rate in the second exhaust passage 32 increases as the reforming catalyst temperature becomes lower. The switching valve 56 is controlled so that the gas path is on the first exhaust passage 31 side. Thereby, after the engine 10 is started, the reforming catalyst of the reforming unit 52 can be activated early.

  On the other hand, if it is determined in S201 that the reforming catalyst temperature T is higher than the reference temperature T1, the controller 60 determines in S204 whether or not the current engine operating state is the reforming EGR execution operating state. . The process of S204 is the same as the process of S104 of FIG. 2 in the first embodiment.

  When it is determined that the reforming EGR execution operation state is set, the controller 60 executes the process of S205. On the other hand, if it is determined that the reforming EGR execution operation state is not established, the controller 60 executes the process of S207.

  In S205, the controller 60 controls the switching valve 56 to open the communication path 55. As a result, the gas path of the second exhaust passage 32 is set on the communication passage 55 side.

  In S206, the controller 60 sets the valve opening timing of the exhaust valve 15 controlled by the variable valve operating system 70 to a predetermined timing based on the reforming EGR rate set for each of the operation regions A to C in FIG. . The opening timing of the exhaust valve 15 is set to advance as the reforming EGR rate increases.

  When the engine 10 is operating in the operation regions A to C of FIG. 4 and the reformed gas is recirculated, an amount of fuel corresponding to the reformed EGR rate is contained in the exhaust in the second exhaust passage 32. The fuel supply unit 53 is controlled so as to be supplied, the opening timing of the exhaust valve 15 is controlled so that the exhaust flow rate is in accordance with the reforming EGR rate, and the gas path of the second exhaust passage 32 is connected to the communication passage 55 side. Set to Thereby, the reformed gas can be recirculated to the intake system, and the combustibility of the air-fuel mixture in the engine 10 can be improved.

  If it is determined in S204 that the reforming EGR execution operation state is not set, the controller 60 controls the switching valve 56 so as to close the communication path 55 in S207. Thereafter, in S208, the controller 60 sets the opening timing of the exhaust valve 15 to a predetermined timing.

  When the engine 10 is operating in the operation region D of FIG. 4 and the reformed gas is not recirculated, the exhaust gas flowing into the second exhaust passage 32 passes through the purification unit 51 and the reforming unit 52 again. It flows into the first exhaust passage 31 and is discharged to the outside together with the exhaust purified by the exhaust purification unit 40 of the first exhaust passage 31.

  After the process of S206 or S208, the controller 60 executes the process of S209. In S209, the controller 60 determines whether or not the reforming catalyst temperature T is higher than the upper limit temperature T2. The upper limit temperature T2 is a temperature set from the viewpoint of preventing thermal degradation of the reforming catalyst, and is set to a value higher than the reference temperature T1.

  When the reforming catalyst temperature T is lower than the upper limit temperature T2, the controller 60 ends the reformed gas recirculation control. On the other hand, when the reforming catalyst temperature T is higher than the upper limit temperature T2, the controller 60 executes the processing after S210.

  In S210, the controller 60 sets the valve opening timing of the exhaust valve 15 controlled by the variable valve operating device 70 based on the reforming catalyst temperature T to a predetermined timing. When the reforming catalyst temperature T is higher than the upper limit temperature T2, the opening timing of the exhaust valve 15 is controlled to be retarded as the reforming catalyst temperature increases. In step S211, the controller 60 controls the switching valve 56 so as to close the communication path 55, and ends the reformed gas recirculation control.

  When the reforming catalyst temperature T is higher than the upper limit temperature T2, the exhaust valve 15 is controlled so that the exhaust flow rate in the second exhaust passage 32 decreases as the reforming catalyst temperature becomes higher. The switching valve 56 is controlled so that the gas path is on the first exhaust passage 31 side. This makes it difficult for exhaust to flow from the first exhaust passage 31 to the second exhaust passage 32, and prevents the temperature of the reforming catalyst in the reforming part 52 from rising too much, thereby preventing thermal deterioration of the reforming catalyst. Is possible.

  According to the reformed gas recirculation apparatus 100 according to the second embodiment described above, the same effects as those of the first embodiment can be obtained.

  In the reformed gas recirculation device 100, the variable valve operating device 70 adjusts the valve opening timing of the exhaust valve 15 to control the exhaust flow rate in the second exhaust passage 32. There is no need to provide a separate adjustment valve. Therefore, the exhaust reforming unit 50 can be brought closer to the engine 10, and the reforming catalyst and the three-way catalyst of the exhaust reforming unit 50 can be activated early.

  Next, with reference to FIG.7 and FIG.8, the modification of the reformed gas recirculation apparatus 100 by 2nd Embodiment is demonstrated. FIG. 7 is a schematic configuration diagram of the reformed gas recirculation device 100 according to the modification, and FIG. 8 is an engine speed-load map relating to the recirculation of the reformed gas.

  As shown in FIG. 7, the reformed gas recirculation device 100 according to the modification includes a recirculation passage 80 that can recirculate part of the exhaust gas flowing through the first exhaust passage 31 to the intake system. The recirculation passage 80 branches from the first exhaust passage 31 on the downstream side of the exhaust purification unit 40 and communicates with the intake passage 20. A control valve 81 for adjusting the flow rate of the exhaust gas flowing into the reflux passage 80 is installed in the reflux passage 80.

  As shown in FIG. 8, in the reformed gas recirculation apparatus 100 according to the modification, the reformed gas reformed in the second exhaust passage 32 is not recirculated to the intake system in the low rotational speed low load operation region E. A part of the exhaust gas flowing through the first exhaust passage 31 is returned to the intake system as external EGR gas. Thus, when performing external EGR, the amount of exhaust gas recirculated to the intake system is controlled by adjusting the exhaust gas flow rate in the recirculation passage 80 according to the opening degree of the control valve 81.

  As described above, in the reformed gas recirculation apparatus 100 according to the modified example, a part of the exhaust gas flowing through the first exhaust passage 31 is recirculated to the intake system in the low rotation speed low load region A. It is possible to improve fuel efficiency over the second embodiment without supplying fuel for generation.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  In the second embodiment, the exhaust flow rate in the second exhaust passage 32 is controlled by the opening timing of the exhaust valve 15, but the exhaust flow rate in the second exhaust passage 32 may be controlled by the lift amount of the exhaust valve 15. . In this case, the exhaust flow rate is increased by increasing the lift amount of the exhaust valve 15, and the exhaust flow rate is decreased by decreasing the lift amount of the exhaust valve 15. The exhaust flow rate may be controlled by adjusting both the opening / closing timing of the exhaust valve 15 and the lift amount.

  In the second embodiment, two exhaust ports 13 are provided for one cylinder, but three or more exhaust ports 13 may be provided for one cylinder. In this case, the reformed gas recirculation device 100 causes the exhaust discharged from the exhaust ports other than the exhaust port where the exhaust valve 15 controlled by the variable valve device 70 is installed to flow through the first exhaust passage 31. Composed.

100 reformed gas recirculation device 10 engine 13 exhaust port 15 exhaust valve 20 intake passage 30 exhaust passage 31 first exhaust passage 32 second exhaust passage 33 exhaust manifold 40 exhaust purification unit 50 exhaust reforming unit 51 purification unit 52 reforming unit 52A Temperature sensor (temperature detector)
53 Fuel supply part 54 Adjustment valve 55 Communication path 56 Switching valve 60 Controller (control part)
61 Crank angle sensor 62 Accelerator pedal sensor 70 Variable valve operating device

Claims (6)

In a reformed gas recirculation device configured to generate reformed gas containing hydrogen from exhaust discharged from an engine and flowing through an exhaust passage, and to recirculate the reformed gas to an intake system,
A first exhaust passage for flowing exhaust exhausted from the engine;
A second exhaust passage for flowing the exhaust discharged from the engine and joining the first exhaust passage on the downstream side;
An exhaust purification unit having a purification catalyst provided in the first exhaust passage on the upstream side of the joining portion where the second exhaust passage joins, and having a purification catalyst capable of purifying exhaust;
A fuel supply section for supplying fuel into the second exhaust passage;
Exhaust gas having a purification catalyst provided in the second exhaust passage and capable of purifying exhaust gas, exhaust gas flowing through the second exhaust passage, and reforming catalyst capable of generating the reformed gas from the fuel supplied from the fuel supply unit A reforming unit;
A communication passage that branches off from the second exhaust passage downstream of the exhaust reforming unit and communicates with the intake system;
An adjustment valve capable of adjusting an exhaust flow rate of the exhaust gas flowing through the second exhaust passage;
A switching valve capable of switching the gas path of the second exhaust passage to the first exhaust passage side or the communication passage side;
And a control unit that controls the adjustment valve and the switching valve. The second exhaust passage is configured to branch from the first exhaust passage on the upstream side of the exhaust purification unit, and to join the first exhaust passage on the downstream side of the exhaust purification unit,
The adjustment valve is provided in the second exhaust passage upstream of the exhaust reforming unit,
2. The reformed gas recirculation apparatus according to claim 1, wherein the switching valve is provided at a branch portion of the second exhaust passage from which the communication passage branches. The engine is
Multiple cylinders,
At least two exhaust ports provided for each cylinder;
An exhaust valve provided in the exhaust port;
A variable valve gear capable of changing at least one of an opening / closing timing and a lift amount of one exhaust valve of each cylinder, and
The second exhaust passage is configured to flow the exhaust discharged from the exhaust port provided with an exhaust valve controlled by the variable valve operating device,
The first exhaust passage is configured to flow the exhaust discharged from the remaining exhaust ports,
The adjusting valve is an exhaust valve controlled by the variable valve operating device,
2. The reformed gas recirculation apparatus according to claim 1, wherein the switching valve is provided at a branch portion of the second exhaust passage from which the communication passage branches. A temperature detection unit for detecting the catalyst temperature of the reforming catalyst;
When the catalyst temperature is higher than a reference temperature, the control unit controls the adjustment valve so that the exhaust flow rate of the second exhaust passage becomes a predetermined flow rate, and the gas path of the second exhaust passage is connected to the communication passage. The reformed gas recirculation apparatus according to any one of claims 1 to 3, wherein the switching valve is controlled so as to be on a passage side.   When the catalyst temperature is lower than the reference temperature, the control unit controls the adjustment valve so that the exhaust flow rate of the second exhaust passage increases as the catalyst temperature decreases, 5. The reformed gas recirculation apparatus according to claim 4, wherein the switching valve is controlled so that a gas path is on the first exhaust passage side.   When the catalyst temperature is higher than an upper limit temperature set higher than the reference temperature, the control unit controls the adjustment valve so that the exhaust flow rate of the second exhaust passage decreases as the catalyst temperature increases. The reformed gas recirculation apparatus according to claim 5 or 6, wherein the switching valve is controlled so that a gas path of the second exhaust passage is on the first exhaust passage side.

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