JP2015151873A - Fuel reformer of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of a fuel reforming catalyst (lowering of fuel reforming performance), and to enhance fuel consumption improvement effect by fuel reformation.SOLUTION: When a prescribed fuel reforming execution condition is established, rich control for controlling an injection amount of main fuel so that an air-fuel ratio of an exhaust gas becomes richer than stoichiometric one, and lean control for controlling the injection amount of the main fuel so that the air-fuel ratio of the exhaust gas becomes leaner than the stoichiometric one are switched to each other alternately at a prescribed cycle. Then, by injecting fuel to be reformed when a rich gas (rich EGR gas) by the rich control passes a reforming fuel injection valve 35, reforming control for reforming the fuel to be reformed by a fuel reforming catalyst 36 is performed. On the other hand, by prohibiting the injection of the fuel to be reformed when a lean gas (lean EGR gas) by the lean control passes the reforming fuel injection valve 35, regeneration control for restoring the fuel reforming performance of the fuel reforming catalyst 36 is performed.

Description

  The present invention relates to a fuel reforming apparatus for an internal combustion engine provided with a fuel reforming catalyst for reforming the fuel of the internal combustion engine.

  As a technique for improving the fuel consumption by reforming the fuel of the internal combustion engine, for example, there is one described in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2009-144612). This is a modification of the reforming fuel injection valve for injecting reforming fuel and the reforming fuel in the middle of the EGR passage for returning a part of the exhaust gas from the exhaust passage of the internal combustion engine to the intake passage as EGR gas. And a fuel reforming catalyst to be improved. Then, the reforming fuel injected by the reforming fuel injection valve and the moisture (water vapor) in the EGR gas undergo a reforming reaction with the fuel reforming catalyst to generate hydrogen and carbon monoxide. The reformed fuel is reformed to generate a reformed gas having high combustibility, and the reformed gas is supplied to the intake passage of the internal combustion engine.

  However, in reforming control in which reforming fuel is reformed by a fuel reforming catalyst, carbon components in the fuel are deposited and deposited on the fuel reforming catalyst. There is a problem in that the amount of carbon deposition of the fuel reforming catalyst increases and the fuel reforming performance of the fuel reforming catalyst decreases.

  Therefore, in Patent Document 1, when the degree of deterioration of the fuel reforming catalyst exceeds the deterioration limit, recovery control for recovering the fuel reforming performance of the fuel reforming catalyst is performed. In this recovery control, the injection of reforming fuel is stopped, the air-fuel ratio of the exhaust gas is controlled to the lean side, and oxygen is supplied to the fuel reforming catalyst to burn carbon deposited on the fuel reforming catalyst. The fuel reforming performance of the fuel reforming catalyst is recovered.

JP 2009-144612 A

  However, in the technique disclosed in Patent Document 1, only the recovery control is executed when the degree of deterioration of the fuel reforming catalyst exceeds the deterioration limit, and the deterioration of the fuel reforming catalyst (decrease in fuel reforming performance) is suppressed. Therefore, the fuel reforming performance deteriorates relatively quickly, and the fuel efficiency improvement effect by the fuel reforming cannot be sufficiently enhanced.

  Therefore, the problem to be solved by the present invention is to provide a fuel reforming apparatus for an internal combustion engine that can suppress deterioration of the fuel reforming catalyst and enhance the fuel efficiency improvement effect by fuel reforming. .

  In order to solve the above problems, the invention according to claim 1 is directed to a main fuel injection means (21) for injecting main fuel supplied to the internal combustion engine (11), and an exhaust passage (23) of the internal combustion engine (11). An EGR passage (32) that recirculates a part of the exhaust gas as EGR gas to the intake passage (12), reforming fuel injection means (35) that injects reforming fuel into the EGR passage (32), A fuel reformer for an internal combustion engine, comprising a fuel reforming catalyst (36) disposed in the EGR passage (32) and reforming the reforming fuel injected by the reforming fuel injection means (35). When a predetermined fuel reforming execution condition is satisfied, rich control for controlling the injection amount of the main fuel so as to make the air-fuel ratio of the exhaust gas rich, and injection of the main fuel so that the air-fuel ratio of the exhaust gas becomes lean Alternates lean control to control the amount at a predetermined cycle In other words, when the rich EGR gas by rich control (hereinafter referred to as “rich gas”) passes through the reforming fuel injection means (35), the reforming fuel is injected and reformed by the fuel reforming catalyst (36). Reforming control is performed to reform the fuel, and when the lean EGR gas by lean control (hereinafter referred to as “lean gas”) passes through the reforming fuel injection means (35), the reforming fuel injection is prohibited. Thus, the control means (37) for executing the regeneration control for restoring the fuel reforming performance of the fuel reforming catalyst (36) is provided.

  In this configuration, the rich control and the lean control are alternately switched, the reforming control is executed when the rich gas by the rich control passes, and the regeneration control is executed when the lean gas by the lean control passes. Quality control and regeneration control can be executed alternately. As described above, by alternately performing the reforming control and the regeneration control, it is possible to suppress deterioration of the fuel reforming catalyst (decrease in fuel reforming performance). As a result, the fuel reforming performance of the fuel reforming catalyst can be maintained at a relatively high state, and the fuel efficiency improvement effect by the fuel reforming can be enhanced.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in one embodiment of the present invention. FIG. 2 is a flowchart (part 1) showing the flow of processing of the reforming control and regeneration control routine. FIG. 3 is a flowchart (part 2) showing the flow of processing of the reforming control and regeneration control routine. FIG. 4 is a time chart for explaining reforming control and regeneration control. FIG. 5 is a diagram for explaining the effect of this embodiment.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 (intake passage) of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and main fuel is injected into the intake port at or near the intake port connected to the intake manifold 20 of each cylinder. A main fuel injection valve 21 (main fuel injection means) is attached. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in each cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

  On the other hand, the exhaust pipe 23 (exhaust passage) of the engine 11 is provided with a catalyst 24 such as a three-way catalyst for purifying exhaust gas, and the exhaust gas air-fuel ratio or rich gas is respectively provided upstream and downstream of the catalyst 24. / Exhaust gas sensors 25 and 26 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean etc. are provided.

  A cooling water temperature sensor 27 that detects the cooling water temperature and a knock sensor 28 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 30 that outputs a pulse signal every time the crankshaft 29 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 29. Based on the output signal of the crank angle sensor 30, the crank angle and engine The rotation speed is detected.

  The engine 11 is equipped with an EGR device 31 that recirculates a part of the exhaust gas from the exhaust pipe 23 to the intake pipe 12 as EGR gas. The EGR device 31 has an EGR pipe 32 (EGR passage) connected between the upstream side of the catalyst 24 in the exhaust pipe 23 and the downstream side of the throttle valve 16 in the intake pipe 12. , An EGR cooler 33 for cooling the EGR gas, and an EGR valve 34 for adjusting the flow rate of the EGR gas are provided. By opening the EGR valve 34, the EGR gas is recirculated from the exhaust pipe 23 to the intake pipe 12 through the EGR pipe 32.

  A reforming fuel injection valve 35 (reforming fuel injection means) for injecting reforming fuel into the EGR pipe 32 is provided on the upstream side of the EGR cooler 33 in the EGR pipe 32. The main fuel injection valve 21 and the reforming fuel injection valve 35 are supplied with fuel from a common fuel tank (not shown). Further, a fuel reforming catalyst 36 for reforming the reforming fuel injected by the reforming fuel injection valve 35 is disposed on the downstream side of the reforming fuel injection valve 35 in the EGR pipe 32. . The fuel reforming catalyst 36 is configured to exchange heat with the exhaust gas flowing in the exhaust pipe 23, and reforms the reforming fuel and moisture (water vapor) in the EGR gas by using the heat of the exhaust gas. By making hydrogen and carbon monoxide react, the reforming fuel is reformed to generate a reformed gas with high combustibility.

  Outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as “ECU”) 37. The ECU 37 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  At this time, the ECU 37 calculates a target EGR rate (target value of the EGR rate) based on the engine operating state when a predetermined EGR control execution condition is satisfied, and the EGR valve 34 so as to realize the target EGR rate. EGR control is performed to control the opening degree. Here, the EGR rate is a ratio of the in-cylinder inflow EGR gas flow rate to the in-cylinder inflow total gas flow rate (= in-cylinder inflow EGR gas flow rate / in-cylinder inflow total gas flow rate).

  The ECU 37 opens the EGR valve 34 and recirculates the EGR gas from the exhaust pipe 24 to the intake pipe 12 through the EGR pipe 32, and supplies the reforming fuel into the EGR pipe 32 by the reforming fuel injection valve 35. The reforming fuel is reformed by injecting and reforming the reforming fuel and moisture (water vapor) in the EGR gas by the fuel reforming catalyst 36 to generate hydrogen and carbon monoxide. A reformed gas having high combustibility is generated, and the reformed gas is supplied to the intake pipe 12.

  However, in the reforming control in which the fuel for reforming is reformed by the fuel reforming catalyst 36, the carbon component in the fuel is deposited and deposited on the fuel reforming catalyst 36. Therefore, as shown by the broken line in FIG. If the quality control is continued, the carbon deposition amount of the fuel reforming catalyst 36 increases with the passage of time and the fuel reforming performance of the fuel reforming catalyst 36 decreases (for example, in the EGR gas recirculated to the intake pipe 12). The concentration of reforming components such as hydrogen and carbon monoxide is reduced).

  Therefore, in this embodiment, the ECU 37 executes reforming control and regeneration control routines shown in FIGS. 2 and 3 to be described later, thereby reforming the reforming fuel with the fuel reforming catalyst 36, and the fuel. Regeneration control for recovering the fuel reforming performance of the reforming catalyst 36 is executed as follows.

  As shown in FIG. 4, when a predetermined fuel reforming execution condition is satisfied, rich control for controlling the injection amount of the main fuel so that the air-fuel ratio of the exhaust gas becomes richer than the stoichiometric, and the exhaust gas empty The lean control for controlling the injection amount of the main fuel is alternately switched at a predetermined cycle so that the fuel ratio is leaner than the stoichiometric ratio.

  Then, reforming control for injecting reforming fuel and reforming reforming fuel by the fuel reforming catalyst 36 when rich gas (rich EGR gas) by rich control passes through the reforming fuel injection valve 35. Execute. In this reforming control, reforming fuel is injected into the EGR pipe 32 by the reforming fuel injection valve 35, and the reforming fuel and moisture (water vapor) in the rich gas are reformed by the fuel reforming catalyst 36. By making hydrogen and carbon monoxide react, the reforming fuel is reformed to generate a reformed gas with high combustibility.

  On the other hand, when lean gas (lean EGR gas) by lean control passes through the reforming fuel injection valve 35, the regeneration control for prohibiting the injection of reforming fuel and restoring the fuel reforming performance of the fuel reforming catalyst 36 is performed. Execute. In this regeneration control, the injection of the reforming fuel is stopped, lean gas is introduced into the EGR pipe 32, and oxygen is supplied to the fuel reforming catalyst 36, so that the carbon deposited on the fuel reforming catalyst 36 is burned. The fuel reforming performance of the fuel reforming catalyst 36 is recovered.

  At this time, in this embodiment, the rich control and the lean control are switched at the reversal timing of the air-fuel ratio in the catalyst 24. Specifically, the control is switched to the lean control at the timing when the air-fuel ratio in the catalyst 24 is reversed to the rich side during the execution of the rich control (for example, the timing when the oxygen adsorption amount of the catalyst 24 becomes equal to or less than the rich determination value). During the execution of the lean control, the control is switched to the rich control at the timing when the air-fuel ratio in the catalyst 24 is reversed to the lean side (for example, the timing when the oxygen adsorption amount of the catalyst 24 becomes equal to or greater than the lean determination value).

  Then, the injection of the reforming fuel is started at the timing when the rich gas by the rich control reaches the reforming fuel injection valve 35, and the reforming fuel at the timing at which the lean gas by the lean control reaches the reforming fuel injection valve 35 (I.e., the reforming fuel is injected until the lean gas reaches the reforming fuel injection valve 35 after the rich gas reaches the reforming fuel injection valve 35).

  In this embodiment, the target EGR rate is changed during reforming control and regeneration control. Specifically, during reforming control, the reforming component concentration in the EGR gas (for example, the concentration of hydrogen or carbon monoxide) is increased, and the combustibility of the engine 11 is improved (that is, the EGR limit is increased). The target EGR rate is made larger than during regeneration control. On the other hand, during the regeneration control, the reforming component concentration in the EGR gas is lowered and the combustibility of the engine 11 is lowered (that is, the EGR limit is lowered), so the target EGR rate is made smaller than during the reforming control.

  However, when the target EGR rate is changed in accordance with switching between reforming control and regeneration control, the target in which the EGR gas flow rate actually corresponds to the target EGR rate after changing the target EGR rate due to the delay in the transfer of EGR gas. There is a delay before changing to the EGR gas flow rate.

  Therefore, in the present embodiment, when the target EGR rate is changed, the injection amount of the reforming fuel and the injection amount of the main fuel are corrected based on the change delay of the EGR gas flow rate due to the delay of the EGR gas transfer. Specifically, when the target EGR rate is changed (increased) in accordance with the switching to the reforming control, the EGR gas flow rate is increased in accordance with the EGR gas transfer delay (shortage with respect to the target EGR gas flow rate). The injection quantity of quality fuel and the injection quantity of main fuel are corrected. On the other hand, when the target EGR rate is changed (decreased) when shifting to the regeneration control (for example, before shifting to the regeneration control), the EGR gas flow rate decreases due to the EGR gas transfer delay (the excess amount relative to the target EGR gas flow rate). Accordingly, the injection amount of the reforming fuel and the injection amount of the main fuel are corrected.

Hereinafter, the processing contents of the reforming control and regeneration control routines of FIGS. 2 and 3 executed by the ECU 37 in this embodiment will be described.
The reforming control and regeneration control routines shown in FIGS. 2 and 3 are repeatedly executed at predetermined intervals during the power-on period of the ECU 37, and serve as control means in the claims. When this routine is started, first, in step 101, it is determined whether or not the fuel reform execution condition is satisfied. For example, the execution condition of EGR control is satisfied (that is, the EGR control is being executed). That is, the determination is made based on whether all the conditions such as the temperature of the fuel reforming catalyst 36 being equal to or higher than the activation temperature are satisfied.

  If it is determined in step 101 that the fuel reforming execution condition is not satisfied, this routine is terminated without executing the processing from step 102 onward.

  On the other hand, when it is determined in step 101 that the fuel reforming execution condition is satisfied, the process proceeds to step 102, where the reforming fuel injection amount (reforming fuel injection amount) is calculated. In this case, the EGR gas flow rate during reforming control is estimated (calculated) based on the target EGR rate during reforming control, and the S / C (ratio of steam to carbon) in the EGR gas during reforming control is the target. The reforming fuel injection amount is calculated so as to be S / C. At this time, the current EGR gas flow rate is estimated (calculated) using a model (formula etc.) simulating the behavior of EGR gas, and the current EGR gas flow rate, the target EGR rate, and the target EGR rate during reforming control are obtained. Based on this, the EGR gas flow rate during the reforming control may be estimated.

  Thereafter, the process proceeds to step 103, and the main fuel injection amount (main fuel injection amount) at the time of rich control is calculated. In this case, the total injection amount (= main fuel injection amount + reforming fuel injection amount) is calculated based on the target air-fuel ratio at the time of rich control, and the difference between the total injection amount and the reforming fuel injection amount is rich. Calculated as the main fuel injection amount during control. The target air-fuel ratio at the time of rich control is set to a value on the rich side with respect to stoichiometry.

  Thereafter, the process proceeds to step 104 and rich control is executed. In this rich control, the injection amount of the main fuel injection valve 21 is controlled to the main fuel injection amount at the time of rich control, and the air-fuel ratio of the exhaust gas is made richer than the stoichiometric.

  Thereafter, the routine proceeds to step 105, where it is determined whether or not it is a rich gas arrival timing (a timing at which the rich gas by the rich control reaches the reforming fuel injection valve 35). In this case, the rich gas arrival timing is estimated (calculated) as follows, for example. The rich gas arrival timing is estimated (calculated) based on the current engine operating state using a model (such as a mathematical expression) that simulates the behavior of the rich gas, or a map that defines the relationship between the engine operating state and the rich gas arrival timing.

  When it is determined in this step 105 that the rich gas arrival timing is reached, the routine proceeds to step 106 where the reforming fuel injection valve 35 starts the reforming fuel injection and executes the reforming control. The rate is changed to the target EGR rate at the time of reforming control.

  During the reforming control, the reforming component concentration in the EGR gas is increased and the combustibility of the engine 11 is improved (that is, the EGR limit is increased). Therefore, the target EGR rate during the reforming control is the same as that during the regeneration control. It is set to a value larger than the target EGR rate during normal control.

  In the reforming control, the injection amount of the reforming fuel injection valve 35 is controlled to the reforming fuel injection amount, the reforming fuel is injected into the EGR pipe 32, and the reforming fuel and moisture in the rich gas are injected. By reforming reaction of (steam) or the like with the fuel reforming catalyst 36 to generate hydrogen or carbon monoxide, the reforming fuel is reformed to generate highly combustible reformed gas.

  At this time, when the target EGR rate is changed (increased) in accordance with the switching to the reforming control, the EGR gas flow rate actually corresponds to the target EGR rate after changing the target EGR rate due to the delay in the transfer of EGR gas. There is a delay before the target EGR gas flow rate changes (increases).

  Therefore, when the target EGR rate is changed (increased) in accordance with the switching to the reforming control, the target S / C is adjusted in accordance with the increase delay of the EGR gas flow rate due to the delay in the transfer of the EGR gas (shortage with respect to the target EGR gas flow rate) The reforming fuel injection amount is corrected to decrease so that the main fuel injection amount is increased accordingly. In this case, the increase delay of the EGR gas flow rate due to the EGR gas transfer delay (deficiency with respect to the target EGR gas flow rate) is estimated (calculated) as follows, for example. An increase in EGR gas flow rate based on the current engine operating state using a model that simulates the behavior of EGR gas (formula etc.) or a map that defines the relationship between the engine operating state and the increase delay in EGR gas flow rate Is estimated (calculated).

  Thereafter, the routine proceeds to step 107, where it is determined whether or not it is the rich side inversion timing of the in-catalyst air-fuel ratio (the timing at which the air-fuel ratio in the catalyst 24 is inverted to the rich side). In this case, for example, the oxygen adsorption amount of the catalyst 24 is estimated, and it is determined whether or not it is the rich-side inversion timing of the air-fuel ratio in the catalyst based on whether or not the oxygen adsorption amount of the catalyst 24 has become equal to or less than the rich determination value. To do.

  When it is determined in step 107 that it is the rich side inversion timing of the air-fuel ratio in the catalyst, the process proceeds to step 108 in FIG. 3, and the target EGR rate is changed to the target EGR rate during regeneration control. During the regeneration control, the reforming component concentration in the EGR gas is lowered and the combustibility of the engine 11 is lowered (that is, the EGR limit is lowered). Therefore, the target EGR rate at the regeneration control is the target at the reforming control. It is set to a value smaller than the EGR rate. As described above, by changing the target EGR rate to the target EGR rate at the time of regeneration control before shifting to regeneration control, it is possible to suppress deterioration of the combustibility of the engine 11 when switching to regeneration control.

  When the target EGR rate is changed (decreased) when shifting to the regeneration control, the EGR gas flow rate actually changes to the target EGR gas flow rate corresponding to the target EGR rate after changing the target EGR rate due to the delay in EGR gas transfer. There is a delay before it changes (decreases).

  Therefore, when the target EGR rate is changed (decreased) when shifting to the regeneration control, the reforming fuel injection amount is set so that the target S / C becomes the target S / C in accordance with the decrease in the EGR gas flow rate due to the EGR gas transfer delay. A decrease correction is made, and the main fuel injection amount is increased by that amount. In this case, the decrease delay of the EGR gas flow rate due to the delay of the EGR gas transfer is estimated (calculated) as follows, for example. Decrease in EGR gas flow rate based on the current engine operating state using a model that simulates the behavior of EGR gas (formula etc.) or a map that defines the relationship between engine operating state and EGR gas flow rate decreasing delay Is estimated (calculated).

  Thereafter, when the EGR gas flow rate converges to the target EGR gas flow rate (when the decrease delay of the EGR gas flow rate becomes almost zero), the routine proceeds to step 109, and the lean control time is based on the target air-fuel ratio at the lean control time. The main fuel injection amount is calculated. The target air-fuel ratio at the time of lean control is set to a value on the lean side with respect to stoichiometry.

  Thereafter, the process proceeds to step 110 to execute lean control. In this lean control, the injection amount of the main fuel injection valve 21 is controlled to the main fuel injection amount at the time of lean control, and the air-fuel ratio of the exhaust gas is made leaner than the stoichiometric.

  Thereafter, the routine proceeds to step 111, where it is determined whether or not it is the lean gas arrival timing (the timing at which the lean gas by the lean control reaches the reforming fuel injection valve 35). In this case, the lean gas arrival timing is estimated (calculated) as follows, for example. The lean gas arrival timing is estimated (calculated) based on the current engine operating state using a model (such as a mathematical expression) that simulates the behavior of lean gas, or a map that defines the relationship between the engine operating state and the lean gas arrival timing.

  When it is determined in this step 111 that the lean gas arrival timing is reached, the routine proceeds to step 112 where the reforming fuel injection at the reforming fuel injection valve 35 is terminated and regeneration control is executed. In this regeneration control, the injection of the reforming fuel is stopped, lean gas is introduced into the EGR pipe 32, and oxygen is supplied to the fuel reforming catalyst 36, so that the carbon deposited on the fuel reforming catalyst 36 is burned. The fuel reforming performance of the fuel reforming catalyst 36 is recovered.

  Thereafter, the routine proceeds to step 113, where it is determined whether or not it is the lean side inversion timing of the in-catalyst air-fuel ratio (the timing at which the air-fuel ratio in the catalyst 24 is inverted to the lean side). In this case, for example, the oxygen adsorption amount of the catalyst 24 is estimated, and it is determined whether or not it is the lean side inversion timing of the air-fuel ratio in the catalyst based on whether or not the oxygen adsorption amount of the catalyst 24 is equal to or greater than the lean determination value. To do.

  When it is determined in step 113 that it is the lean side inversion timing of the air-fuel ratio in the catalyst, this routine is finished. If it is determined in step 101 that the fuel reforming execution condition is satisfied, the processes in steps 102 to 113 are repeated.

  In the present embodiment described above, the rich control that makes the exhaust gas air-fuel ratio rich and the lean control that makes the exhaust gas air-fuel ratio lean are alternately performed at predetermined intervals when a predetermined fuel reforming execution condition is satisfied. Switch to. Then, reforming control for injecting the reforming fuel when the rich gas by the rich control passes through the reforming fuel injection valve 35 and reforming the reforming fuel by the fuel reforming catalyst 36 is executed. On the other hand, regeneration control is performed to restore the fuel reforming performance of the fuel reforming catalyst 36 by prohibiting the injection of reforming fuel when the lean gas by the lean control passes through the reforming fuel injection valve 35.

  In this way, the reforming control and the regeneration control can be executed alternately. By alternately executing the reforming control and the regeneration control, the deterioration of the fuel reforming catalyst 36 (of the fuel reforming performance) can be performed. Reduction) can be suppressed. As a result, as shown by a solid line in FIG. 5, the fuel reforming performance of the fuel reforming catalyst 36 is relatively high (for example, reforming components such as hydrogen and carbon monoxide in the EGR gas recirculated to the intake pipe 12). Can be maintained at a relatively high concentration), and the fuel efficiency improvement effect by fuel reforming can be enhanced.

  In this embodiment, the control is switched to the lean control at the timing when the air-fuel ratio in the catalyst 24 is reversed to the rich side during the execution of the rich control, and the air-fuel ratio in the catalyst 24 is reversed to the lean side during the execution of the lean control. Switch to rich control at the timing. In this way, the state in the catalyst 24 (for example, the oxygen adsorption amount) can be maintained within an appropriate range, and deterioration of the exhaust gas purification rate of the catalyst 24 can be suppressed.

  Further, in this embodiment, the injection of reforming fuel is started at the timing when the rich gas by the rich control reaches the reforming fuel injection valve 35, and the timing at which the lean gas by the lean control reaches the reforming fuel injection valve 35 Thus, the injection of the reforming fuel is terminated. In this way, the reforming fuel is injected only during the period during which the rich gas passes through the reforming fuel injection valve 35, and the reforming fuel is injected during the period during which the lean gas passes through the reforming fuel injection valve 35. You can stop it. Accordingly, it is possible to prevent the reforming fuel from being injected into the lean gas and suppress the oxidation reaction between the reforming fuel and the lean gas.

  In the present embodiment, the target EGR rate is changed between reforming control and regeneration control. Specifically, during the reforming control, the reforming component concentration in the EGR gas is increased and the combustibility of the engine 11 is improved (that is, the EGR limit is increased). Therefore, the target EGR rate is set to be higher than that during the regeneration control. I try to make it bigger. Thereby, the fuel consumption improvement effect during reform control can be heightened. On the other hand, during the regeneration control, the reforming component concentration in the EGR gas is lowered and the combustibility of the engine 11 is lowered (that is, the EGR limit is lowered), so that the target EGR rate is made smaller than during the reforming control. I have to. Thereby, deterioration of combustion during regeneration control can be suppressed.

  Further, in the present embodiment, when the target EGR rate is changed (increased) in accordance with the switching to the reforming control, the increase in EGR gas flow rate due to the EGR gas transfer delay (shortage with respect to the target EGR gas flow rate) is caused. At the same time, the injection amount of the reforming fuel and the injection amount of the main fuel are corrected. This prevents the actual S / C from deviating from the target S / C due to a delay in the increase in the EGR gas flow rate when the target EGR rate is changed (increased) with the switching to the reforming control. it can.

  On the other hand, when the target EGR rate is changed (decreased) when shifting to the regeneration control, the injection amount of the reforming fuel and the injection amount of the main fuel are set in accordance with the decrease in the EGR gas flow rate due to the delay in the EGR gas transfer. I am trying to correct it. This can prevent the actual S / C from deviating from the target S / C when the target EGR rate is changed (decreased) when shifting to the regeneration control.

  In the above embodiment, the rich control and the lean control are switched at the inversion timing of the air-fuel ratio in the catalyst 24. However, the present invention is not limited to this. For example, at the inversion timing of the air-fuel ratio downstream of the catalyst 24. You may make it switch between rich control and lean control. Specifically, the timing at which the air-fuel ratio on the downstream side of the catalyst 24 is reversed to the rich side during execution of the rich control (for example, the timing at which the detected air-fuel ratio on the downstream side of the catalyst 24 becomes equal to or less than the rich determination value) ) To switch to lean control. During the execution of the lean control, the rich control is performed at the timing when the air-fuel ratio downstream of the catalyst 24 is reversed to the lean side (for example, the timing when the detected air-fuel ratio of the exhaust gas sensor 26 downstream of the catalyst 24 is equal to or greater than the lean determination value). Switch to.

Alternatively, the rich control and the lean control may be switched every predetermined time or every predetermined number of injections.
In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1, but includes an in-cylinder injection type engine, and both an intake port injection fuel injection valve and an in-cylinder injection fuel injection valve. It can also be applied to dual-injection engines.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 21 ... Main fuel injection valve (main fuel injection means), 23 ... Exhaust pipe (exhaust passage), 24 ... Catalyst, 32 ... EGR piping (EGR passage) ), 35 ... Reforming fuel injection valve (reforming fuel injection means), 36 ... Fuel reforming catalyst, 37 ... ECU (control means)

Claims (5)

A main fuel injection means (21) for injecting main fuel supplied to the internal combustion engine (11), and an intake passage (12) using EGR gas as a part of exhaust gas from the exhaust passage (23) of the internal combustion engine (11). An EGR passage (32) for recirculation, reforming fuel injection means (35) for injecting reforming fuel into the EGR passage (32), and the reforming fuel disposed in the EGR passage (32). A fuel reformer for an internal combustion engine, comprising a fuel reforming catalyst (36) for reforming the reforming fuel injected by the fuel injection means (35).
The rich control for controlling the injection amount of the main fuel so as to make the air-fuel ratio of the exhaust gas rich when the predetermined fuel reforming execution condition is satisfied, and the air-fuel ratio of the exhaust gas so as to be lean When the lean control for controlling the injection amount of the main fuel is alternately switched at a predetermined cycle, rich EGR gas (hereinafter referred to as “rich gas”) by the rich control passes through the reforming fuel injection means (35). A reforming control for injecting the reforming fuel and reforming the reforming fuel with the fuel reforming catalyst (36) is performed, and lean EGR gas (hereinafter referred to as “lean gas”) by the lean control is generated. Control means for executing regeneration control for restoring the fuel reforming performance of the fuel reforming catalyst (36) by prohibiting injection of the reforming fuel when passing through the reforming fuel injection means (35). 37) And the fuel reforming device of the internal combustion engine, characterized in that are. A catalyst (24) for purifying exhaust gas of the internal combustion engine (11);
The control means (37) switches between the rich control and the lean control at an inversion timing of an air-fuel ratio in the catalyst (24) or an inversion timing of an air-fuel ratio downstream of the catalyst (24). The fuel reformer for an internal combustion engine according to claim 1.   The control means (37) starts injection of the reforming fuel at a timing when the rich gas reaches the reforming fuel injection means (35), and the lean gas becomes the reforming fuel injection means (35). The fuel reforming apparatus for an internal combustion engine according to claim 1 or 2, wherein the injection of the reforming fuel is terminated at a timing when the pressure reaches the engine.   The internal combustion engine fuel reformer according to any one of claims 1 to 3, wherein the control means (37) changes a target EGR rate during the reforming control and during the regeneration control.   The control means (37) is configured to determine whether the reforming fuel injection amount and the main fuel injection amount are based on a change delay of the EGR gas flow rate due to a delay in the transfer of the EGR gas when the target EGR rate is changed. The fuel reformer for an internal combustion engine according to claim 4, wherein at least one of the two is corrected.

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